BULIT 6 muffled with hum

Bought a pair of BULIT 6 reference monitors about a couple years ago. For the most part my experience with them had been great. Recently I’ve had an issue with one where my sound has become muffled in one and has a buzz. Took it to a pioneer certified repair place and had the amp replaced. Worked fine for a couple weeks and brought it back thinking the issue stemmed from the recent repair. Took it to the repair shop and each time they can’t replicate the issue. Took it home thinking maybe it’s cables or positioning and the issue is still present. Changed out the power cable, audio source and position and the issue is present in all applications including directly to my turntables. Other monitor works fine with the same applications. Any idea what the issue might be? I’ve run out of possible troubleshooting options to resolve the issue.