Bluetooth runs on the 2.4GHz radio spectrum, as do many other devices which could cause interference. Sources can be from microwave ovens, cordless telephones on 2.4GHz band, WiFi on 2.4GHz, etc. It may originate from your house/apartment or a very close neighbor. If you notice a coincidence when the mouse glitch occurs (phone ringing, microwave in use) that might be the culprit. If your WiFi is on 2.4GHz, try changing the channel, or even better, move it to the 5GHz band if possible.
Might also be a bad location for the Mini where the internal antenna is shielded by metal surroundings between it and the mouse. If you have disassembled the Mini be sure the antenna was reattached properly.
... or it could simply be a bad mouse ...
-howard