Hello sorry it's been a while. I have crawled this thread entirely: /t5/Xperia-Z5-Z5-Compact-Z5-Premium/Bluetooth-audio-stutter-after-marshmallow-update/td-p/1103796/pa... and I think it's basically the same problem.
I have tried in safe mode playing music with the only built-in music app through aptX to my bluetooth speaker, initially there are absoultly no problem (because it has few apps/services running, of course...) until I intentionaly open dozens of memory-consuming tabs in chrome and run as many apps as I can at the same time, the stutter does occur in safe mode only less frequently than normal mode. I'm no engineer so I'm not capable of reading system logs in any means, so I can only guess that it has something to do with system resourse consumption or with the processing priority of BT audio.
Some people in the thread above says it is a problem about the firmware/hardware of the FM/BT chip and sony has tested to shut down the radio feature to get BT audio works fine, well if that is true than I am willing to give up the FM radio feature, because the HiFi bluetooth audio of Z4T is one of the main reasons I bought it!
