Bluetooth intermittently cutting out

I have a Acer Liquid Z630 5.5" unlocked smartphone.

The bluetooth sound keeps intermittantly cutting out - specifically, there are very short gaps of silence about every 30 seconds or so where the sound cuts out for a fraction of a second.

This happens on all Bluetooth speakers and headsets I have tested. It does not happen with an older Samsung Galaxy smartphone.

I have tried restoring the phone to its factory settings, and removing and adding back the phone as a device, but nothing works.

I suspect this is a problem with the phone hardware/firmware or Bluetooth driver and am wondering if there are any specific updates or patches that could help.