I've always found the strict voltage tolerance for the G68 surprising. I suspect (but have zero evidence for) that the voltage dropping from 5.1 to 5.0 is a symptom of a failing PSU and that considerably greater fluctuations occur when the unit is working hard and the PSU is under load.

Main system - Sources (Kodi-HTPC, Vero 4k, FireTV, Sat) into Trinnov Altitude 32 (8-16) (+Roon), Trinnov Amplitude 8 amp & Vivid Audio (Giya G3, V1.5) and REL Stentor III speakers. Others: F80 + Raspberry Pi and other Pi systems.