Hi,
I have similar problems with Ubuntu Mate.
My applicaton requires data exhange between 2 systems.
System 1: Raspberry Pi3, Ubuntu Mate 16.04
System 2: Laptop PC, Ubuntu 16.04 LTS
These systems exchange text buffers using bluetooth sockets.
Ubuntu Mate (on Rasp.Pi) freezes after some time, (some minutes, faster if I use a mouse).
There are few ways to continue, the magic key sysRq-B boots, it is the only sysRq key which works.
… a CTRL-ALT-F1 opens the linux screen where I can do some stuff … some minutes later this system also freezes.
… I was able to see in Linux screen that the bluetooth connection address became 00:00:00:00:00:00.
After a clean restart (power off, on), if I open the linux screen (CTRL-ALT-F1) and launch my application, everything works fine.
No freeze, no hang-up. My bluetooth communication works fine.
This is OK for me, the Raspberry device will be a used to execute commands coming from bluetooth.
I hope this gives you some hints.
Best.