Can you also try briefly using a single thread for audio? EngineBehaviour::getNumberOfCPUsToUseForAudio()
I’m wondering if the thread scheduling or use of efficiency cores is stalling the processing.
I also know there’s some code to use the audio thread for as long as the buffer is. That used to be recommended behaviour for Android. Not sure if its still necessary. If not, maybe comment out the JUCE_ANDROID code in tracktion_DeviceManager.cpp?