Does this distortion only occur in combination with logic? How is it with other audio sources like audio player or DAWs?

I ask because it could also be related to the Logic update.

The problem may not necessarily be the RME card/driver, but hard to say exactly what it is so I'm approaching from different fronts.

I have two computers using HDSPe PCIe cards in Logic 12.3, and only one of them (mac mini M2) seems to be experiencing this issue.

The other computer is an m3 Mac Studio, running HDSPe MADI.  The mac mini m2 receives the MADI into Logic 12.3 (buffer of 64) and outputs via SPDIF from RAYDAT to monitors.  This has worked flawlessly for years on both this setup and older setups, until the logic 12.3 update.

After I updated to Logic 12.3 (in OS26.6)and experienced this issue of distortion, I noticed my RME driver was out of date by one version.  Updating the driver had no effect.

And while it may seem like updating Logic is the most likely cause, it didn't seem to affect my Mac Studio at all.  Restarting Logic on the mac mini fixes the issue temporarily (until it returns).

My HDSPe cards are running in Sonnet Express enclosures purchased at the same time, and these receive power from a Black Lion PG-2 power conditioner, they are clocked by an external wordclock (internally connected between RayDAT and MADI on the m2).

The problematic effect sounds like a bad clocking error, digital distortion to various degrees of awfulness.