Presonus Digimax DP88 8 Channel Mic Preamp, Issue With Inputs 7/8, See Descrip

Bought in 2018 from ProAudioStar, I've been the only owner. Since the beginning of using this unit, I've had noise on inputs/outputs 7/8, but I've been able to use the rest of the inputs/outputs with no issue on recordings. It sounds like sample rate mismatch noise, so it's possible I've just been using a faulty ADAT cable or some other issue beyond the scope of the unit.

UPDATE: Someone asked me to describe the issue with I/O 7/8 in more detail. Intermittent clicks/pops as opposed to scratchy noise - what I would describe as noise you hear when you have a clock mismatch between master and slave. There would be times when I thought the issue was resolved but then it would reappear. It never affected any of the other input/output channels - I felt comfortable mixing/tracking records just using I/O 1-6. I tried using both word clock and ADAT connection but nothing seemed to be a solid fix.

I use an RME interface - it's possible the issue was something related to my interface or cables I was using, but I can't say for a fact.