Finder hanging on click-to-play audio files without opening them in iTunes or other App.

I have Mojave on a couple of 2018 Minis - Suddenly i've noticed erratic things. I produce commercials and other content for a living and VERY regularly use the feature where you can simply click on an audio file icon with the spacebar and playback the audio through whatever your System Audio is configured for playback.

Recently, in going through a larger number of files to check them, there is an indefinite hang where the file won't open and 'resolve' to the player window. At this point it's inconsistent. It restores to normal for a period of time but then can reoccur. What I've tried, to temporarily restore it was, reboot, an SMC reset, PRAM reset, disk utility first aid.

I have an external HD that i "write" to - my internal HD is APFS formatted, the external is HFS+. I ran

Malwarebytes and it showed no corruption. I noticed that my external HD is randomly not mounting or showing up in Disk Utility. It does with a restart.. and then later for some reason the icon on the desktop -isn't there - and drive not mounted. Once I tried swapping the cable over to another USB 3.2 port, and the drive reappeared.

The 'preview' playback capability randomly can just stops responding - like... suddenly the next file i hit after a dozen of them in quick succession - just spirals with the gear icon indefinitely. I thought perhaps it was limited to files on the external HD, but i noticed it with some files on the internal/main drive too so...figure it kinda rules out a hardware issue...or..?? Thanks for any ideas.