Build: 3.0, AI-171.4408382, 201710201707,

AI-171.4408382, JRE 1.8.0_152-release-915-b01x64 JetBrains s.r.o, OS Windows 10(amd64) v10.0 , screens 1920x1080

IMPORTANT: Please read https://developer.android.com/studio/report-bugs.html carefully and supply all required information.

Gradle Version: 4.1
Android Plugin Version: 3.0.0
TargetSDK (compiledSDK): 26
MinSDK: 21
Build Tools Version: 27.0.0 (latest - using default setting which points to latest installed)
Android SDK Tools: 26.1.1

Project Setup:
I have a project containing 5 .aar libraries (resources, toolbox, ui, web, race). - see screenshot1
It is using two build flavors: "api21" and "api17". The name tells the minimum sdk. - see screenshot2
buildConfigs are standard: debug and release, minifyEnabled=false on .aar level (I minify on apk level in the app-project)
Funny thing: The error below tells me something about "layout-v16" ... My minSdk is set to 21! I do not have a single piece of code/xml that points to anything below api17!

How to reproduce:
* start the "assembly" task FOR THE FIRST TIME, it runs through without error.
* Then change something in the xml "themes.xml" or "styles.xml" of the resources library (which contains only xml - no java code)
* try to assemble again -> see crash below
I can reproduce it 100% of the time.
Happens only (as far as i can tell) when xml resources are changed. Java code changes cause no harm here.

How to solve:
* I am forced to do a "Rebuild project" manually (Build -> Rebuild project), then "assemble" will work again ... for ONE RUN. Then again "rebuild project" is forced. This consumes lots of time...

Even worse: What happens in the APP project that uses this library?
* After EVERY new "assemble" of the library, I can not build the app.
* Only solution (and this is cruel): File -> Invalidate caches and restart - I have to do this EVERY TIME, a new version of the library is assembled!
* it seems, there are (too?) many things cached from aar references.
* When I click the "run" button to deploy the app to my emulator, gradle tells me:
Executing tasks: [:app:assembleDebug]
Configuration 'compile' in project ':app' is deprecated. Use 'implementation' instead.
??
build.gradle for my app: contains this block for the references to my .aars:
compile(name:'race-api21-release', ext:'aar')
compile(name:'resources-api21-release', ext:'aar')
compile(name:'toolbox-api21-release', ext:'aar')
compile(name:'ui-api21-release', ext:'aar')
compile(name:'web-api21-release', ext:'aar')

Here is the complete stacktrace from my gradle console - LIBRARIES PROJECT

:ui:verifyApi21ReleaseResources FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':ui:verifyApi21ReleaseResources'.
> com.android.builder.internal.aapt.AaptException: Failed to compile file C:\Work\Dev\Git\and-platform\ui\build\intermediates\res\merged\api21\release\layout-v16

* Try:
Run with --info or --debug option to get more log output.

* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':ui:verifyApi21ReleaseResources'.
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:100)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:70)
at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:63)
at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54)
at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:88)
at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.java:52)
at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:54)
at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:34)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.run(DefaultTaskGraphExecuter.java:248)
at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:197)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:107)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:241)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:230)
at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.processTask(DefaultTaskPlanExecutor.java:124)
at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.access$200(DefaultTaskPlanExecutor.java:80)
at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:105)
at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:99)
at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.execute(DefaultTaskExecutionPlan.java:625)
at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.executeWithTask(DefaultTaskExecutionPlan.java:580)
at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.run(DefaultTaskPlanExecutor.java:99)
at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
Caused by: org.gradle.internal.UncheckedException: com.android.builder.internal.aapt.AaptException: Failed to compile file C:\Work\Dev\Git\and-platform\ui\build\intermediates\res\merged\api21\release\layout-v16
at org.gradle.internal.UncheckedException.throwAsUncheckedException(UncheckedException.java:63)
at org.gradle.internal.UncheckedException.throwAsUncheckedException(UncheckedException.java:40)
at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:76)
at org.gradle.api.internal.project.taskfactory.DefaultTaskClassInfoStore$IncrementalTaskAction.doExecute(DefaultTaskClassInfoStore.java:173)
at org.gradle.api.internal.project.taskfactory.DefaultTaskClassInfoStore$StandardTaskAction.execute(DefaultTaskClassInfoStore.java:134)
at org.gradle.api.internal.project.taskfactory.DefaultTaskClassInfoStore$StandardTaskAction.execute(DefaultTaskClassInfoStore.java:121)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$1.run(ExecuteActionsTaskExecuter.java:122)
at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:197)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:107)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:111)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:92)
... 27 more
Caused by: com.android.builder.internal.aapt.AaptException: Failed to compile file C:\Work\Dev\Git\and-platform\ui\build\intermediates\res\merged\api21\release\layout-v16
at com.android.build.gradle.tasks.VerifyLibraryResourcesTask.compileResources(VerifyLibraryResourcesTask.java:190)
at com.android.build.gradle.tasks.VerifyLibraryResourcesTask.compileAndVerifyResources(VerifyLibraryResourcesTask.java:146)
at com.android.build.gradle.tasks.VerifyLibraryResourcesTask.doIncrementalTaskAction(VerifyLibraryResourcesTask.java:107)
at com.android.build.gradle.internal.tasks.IncrementalTask.taskAction(IncrementalTask.java:113)
at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:73)
... 37 more