Ultralite MK3 Hybird (USB) Playback skipping/glitching - sample rate mismatch?

[GrizzlyAK]

I have experienced this for a long time, and have tried to figure out the cause but, sometimes, when I play back from certain applications like Soundcloud in my Firefox browser or, most recently, Apple Music, the playback glitches at regular intervals. Some playback in Firefox, like from YouTube works OK. So does Windows Media Player and MPC-HC. If I route the sound from apps that glitch to a different soundcard, say my HP monitor with built-in speakers, it plays back fine. So I know it has something to do with my MOTU, I just don't know what or how to work around it. I typically have my sample rate set to 48kHz, since that is what I use in my DAWs (which never exhibit this behavior).

I can sometimes manually change the sample rate to 44.1kHz using Audio Console (when I figure out how to launch it - it's temperamental) and it sounds better, glitching much less, but still glitches seemingly regularly at fewer intervals further apart, and not as apparent. So I don't think it is 100% a sample rate issue, but I do notice the pitch difference in the playback at the different rates. The typical glitching is very apparent and is unlistenable, which makes some apps unable to utilize my main speakers connected to my MOTU. As I look to potentially upgrade my Audio Interface in the future, I am considering MOTU again, but would like to understand this phenomenon before I commit. Any idea as to why this is happening and how to avoid it?