I've started receiving this crash under crashlytics since upgrading to Cast SDK 3. I don't know how to reproduce it, it has never happened to me. I'm guessing I'm doing something wrong, but I don't see any of my code on the stacktrace. How can I figure out where the issue is?

Which version of the Cast SDK are you using? Cast SDK 3 - I'm targeting Google Play Services 15

Fatal Exception: java.lang.IllegalStateException: GoogleApiClient is not connected yet.
at com.google.android.gms.common.api.internal.zzaj.execute(Unknown Source)
at com.google.android.gms.common.api.internal.zzbd.execute(Unknown Source)
at com.google.android.gms.common.api.internal.zzav.execute(Unknown Source)
at com.google.android.gms.cast.Cast$CastApi$zza.sendMessage(Unknown Source)
at com.google.android.gms.cast.framework.media.RemoteMediaClient$zza.zza(Unknown Source)
at com.google.android.gms.internal.cast.zzcm.zza(Unknown Source)
at com.google.android.gms.internal.cast.zzdh.zza(Unknown Source)
at com.google.android.gms.internal.cast.zzdh.zzda(Unknown Source)
at com.google.android.gms.internal.cast.zzdh.zza(Unknown Source)
at com.google.android.gms.internal.cast.zzdi.zza(Unknown Source)
at com.google.android.gms.internal.cast.zzdn.zza(Unknown Source)
at com.google.android.gms.internal.cast.zzdn.zza(Unknown Source)
at com.google.android.gms.internal.cast.zzdn.zzdc(Unknown Source)
at com.google.android.gms.internal.cast.zzdo.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:241)
at android.app.ActivityThread.main(ActivityThread.java:6274)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)