We've rebuilt https://github.com/TheLastProject/ShareToInputStick/releases/tag/v3.6.1 multiple times (each time in a fresh container): with 2, 4, 6, 8, and 16 cores available, respectively.

Depending on the number of cores, we get a different classes.dex file and thus a different APK, which breaks Reproducible Builds:

With 2 and 4 cores we always get an unsigned APK with SHA-256 14763d682c9286ef65323d9eb947240ac62941938ac6f9048bdf880019fb3ee9.
with 6, 8, and 16 cores we get an unsigned APK with SHA-256 35324ba4c4927607415b5d5a9c56bcf0d557aad285a3d78b72365b143b1cb60e instead.

The only difference is the classes.dex file (and of course the baseline.prof as it contains a checksum of the .dex); the dexdump diff is very small:

@@ -2,9 +2,9 @@
 Opened 'classes.dex', DEX version '035'
 DEX file header:
 magic               : 'dex\n035\0'
-checksum            : 5c51b34f
-signature           : f062...4a1d
-file_size           : 9889456
+checksum            : 7df369bb
+signature           : 155e...3e08
+file_size           : 9889452
 header_size         : 112
 link_size           : 0
 link_off            : 0 (0x000000)
@@ -20,7 +20,7 @@
 method_ids_off      : 808120 (0x0c54b8)
 class_defs_size     : 7247
 class_defs_off      : 1331088 (0x144f90)
-data_size           : 8326464
+data_size           : 8326460
 data_off            : 1562992 (0x17d970)
 
 access_flags        : 1537 (0x0601)
@@ -1309293,23 +1309293,22 @@
       registers     : 7
       ins           : 4
       outs          : 4
-      insns size    : 57 16-bit code units
+      insns size    : 55 16-bit code units
 | com.inputstick.api.BTConnectionManager.connect:(ZIZ)V
 |: invoke-virtual {v3}, Lcom/inputstick/api/BTConnectionManager;.resetErrorCode:()V
 |: iget-object v0, v3, Lcom/inputstick/api/BTConnectionManager;.mBTService:Lcom/inputstick/api/bluetooth/BTService;
-|: if-nez v0, 0022 // +001d
+|: if-nez v0, 0020 // +001b
 |: new-instance v0, Lcom/inputstick/api/bluetooth/BTService;
 |: iget-object v1, v3, Lcom/inputstick/api/BTConnectionManager;.mApp:Landroid/app/Application;
 |: iget-object v2, v3, Lcom/inputstick/api/BTConnectionManager;.mBTHandler:Lcom/inputstick/api/BTConnectionManager$BTHandler;
 |: invoke-direct {v0, v1, v2}, Lcom/inputstick/api/bluetooth/BTService;.<init>:(Landroid/app/Application;Landroid/os/Handler;)V
 |: iput-object v0, v3, Lcom/inputstick/api/BTConnectionManager;.mBTService:Lcom/inputstick/api/bluetooth/BTService;
-|: new-instance v0, Lcom/inputstick/api/PacketManager;
-|: iget-object v1, v3, Lcom/inputstick/api/BTConnectionManager;.mBTService:Lcom/inputstick/api/bluetooth/BTService;
+|: new-instance v1, Lcom/inputstick/api/PacketManager;
 |: iget-object v2, v3, Lcom/inputstick/api/BTConnectionManager;.mKey:[B
-|: invoke-direct {v0, v1, v2}, Lcom/inputstick/api/PacketManager;.<init>:(Lcom/inputstick/api/bluetooth/BTService;[B)V
-|: iput-object v0, v3, Lcom/inputstick/api/BTConnectionManager;.mPacketManager:Lcom/inputstick/api/PacketManager;
-|: iget-object v1, v3, Lcom/inputstick/api/BTConnectionManager;.mInitManager:Lcom/inputstick/api/init/InitManager;
-|: invoke-virtual {v1, v3, v0}, Lcom/inputstick/api/init/InitManager;.init:(Lcom/inputstick/api/init/InitManagerListener;Lcom/inputstick/api/PacketManager;)V
+|: invoke-direct {v1, v0, v2}, Lcom/inputstick/api/PacketManager;.<init>:(Lcom/inputstick/api/bluetooth/BTService;[B)V
+|: iput-object v1, v3, Lcom/inputstick/api/BTConnectionManager;.mPacketManager:Lcom/inputstick/api/PacketManager;
+|: iget-object v0, v3, Lcom/inputstick/api/BTConnectionManager;.mInitManager:Lcom/inputstick/api/init/InitManager;
+|: invoke-virtual {v0, v3, v1}, Lcom/inputstick/api/init/InitManager;.init:(Lcom/inputstick/api/init/InitManagerListener;Lcom/inputstick/api/PacketManager;)V
 |: iget-object v0, v3, Lcom/inputstick/api/BTConnectionManager;.mBTService:Lcom/inputstick/api/bluetooth/BTService;
 |: invoke-virtual {v0, v5}, Lcom/inputstick/api/bluetooth/BTService;.setConnectTimeout:(I)V
 |: iget-object v5, v3, Lcom/inputstick/api/BTConnectionManager;.mBTService:Lcom/inputstick/api/bluetooth/BTService;
@@ -1309323,10 +1309322,10 @@
       catches       : (none)
       positions     : 
       locals        : 
-        0x0000 - 0x0039 reg=3 this Lcom/inputstick/api/BTConnectionManager; 
-        0x0000 - 0x0039 reg=4 (null) Z 
-        0x0000 - 0x0039 reg=5 (null) I 
-        0x0000 - 0x0039 reg=6 (null) Z 
+        0x0000 - 0x0037 reg=3 this Lcom/inputstick/api/BTConnectionManager; 
+        0x0000 - 0x0037 reg=4 (null) Z 
+        0x0000 - 0x0037 reg=5 (null) I 
+        0x0000 - 0x0037 reg=6 (null) Z 
 
     #4              : (in Lcom/inputstick/api/BTConnectionManager;)
       name          : 'disconnect'

Version of Gradle Plugin: 8.6.0
Version of Gradle: 8.7
Version of Java: OpenJDK 17
OS: Debian bookworm