Hello!
I have exactly the same issue. Bluetooth for my Z3+ constantly switches itself off and on and connection to my other bluetooth devices is lost. I'm already pretty frustrated. I had the same issue with previous Sony Xperia Z3. I hoped that Z3+ would be better, but seems not. I also tried with factory reset and no success. I would even say it's a little dangerous as I have experienced the bluetooth connectivity lost during driving my car with bluetooth headphones and when suddenly connection i lost I have to reach out for my phone and it happens even several times during one phonecall.
What can be done to fix it? Is there a way to determine what happens by some logs where bluetooth related connections are logged? Is there somekind of program for that? So far I haven't found any really useful tools. If I'd send my phone to repair shop, I probably have to do it several times, as mostly nothing is really checked after they send it back first time. And I need my phone during that time what might take more than 2 weeks...
I've owned so far 3 Sony phones and seems that this one is going to be the last one... unfortunately. I like it and it's waterproof and so on, but issues with bluetooth connectivity and the issue with overheating when for example recording even short video is not really acceptable thing.
