Audio mix presets are messing up playback

iMac (Retina 5K, 27-inch, 2020)
64gb Memory
Big Sur
Final Cut Pro X - 10.5.4
Original files are on Lacie 2Big
Library on separate Lacie 2Big
Lacie drives are daisy chained

I've had a problem for some time where my audio is going screwy. When I hit play on the timeline the audio will often go juddery, repeat like Max Headroom (or Kryten after an acid beer) and go out of sync until I stop and start the playhead. It's infuriating. It's also very inconsistent. Sometimes I can play an entire 30 minute video with no issues. But 75% of the time as soon as I hit play it starts going weird. The image remains normal, it's just the audio that gets stuck on one frame for a few seconds before continuing (at which point it's out of sync but only during that playback). 

I spent a long time trying to figure out what's causing it - and I finally figured out it's the Effects Presets that I drop onto my audio. I have a few mixes I use depending on which mic I am playing with. The presets are stored in a folder somewhere on my Mac. 

Has anyone experienced this before? And does anyone have any advice for how to proceed? I don't know where else I could possibly put the presets (even if I knew how to do that). 

Any help would be gratefully received. I spend 12 hours a day working on this stuff and really need to make it less painful! 

Couple of questions:
- How did you create these presets, and how did you get them into the mystery folder?
- How do you apply them? Are you dragging & dropping from the Finder to your timeline?

I followed the instructions of a guy on YouTube and after adding them (a combination of Compressor, Limiter and Channel EQs) I hit 'Save Effects Preset' and now they appear in the Apple folder on Audio Effects.

If I right click on the settings in the FCPX audio effects browser, I can reveal in finder. Whereby I am taken to a folder called Effects Presets, although I cannot find that folder any other way (it doesn't show up on Spotlight).

Your presets folder would be HD / Users / home / Library (invisible by default) / Application Support / Pro Apps / Effects Presets

The name 'Apple' in your audio effects browser is just a group name that you would've created when you made the first custom preset. These presets are XML files that store and apply the settings and filters present in the originating clip, so in theory, if you were to manually apply each of the effects to a clip, you should get the same janky playback. Is this the case?

Would you be willing to post one of your preset files for a closer look?