Issues with Plex server buffering after restoring backup to new hard drive

Hi all. I posted this on the Reddit sub forum but thought it was probably worth asking everyone here as well.

I’m running a 2012 Mac Mini Plex server Version 1.5.3.3580.
I am using ACDCLI as a mount for my videos and stream Plex to clients in the house, primarily an ATV4. I was having very few issues with this setup. My hard drive in the Mac Mini died and I had to replace it. I restored from a Time Machine backup I had that sadly was a few months behind. I replaced with a Samsung SSD if it matters.
Anyway, the restore went off without a hitch. Now however, streaming my movies gives me severe buffering at multiple points. It will play and sometimes get 30-50 minutes in to a movie but then will start buffering badly, giving me a spinning wheel next to the timeline. It may play for 5-10 seconds and then freeze again. This is noticeably worse than before I had to replace the hard drive. when it freezes it freezes hard (i.e. freezes for up to a minute, plays for 5 seconds then freezes again, etc).
The server logs are very comprehensive. Can someone point me to what i should be looking for to tell if it’s a problem with the Plex install, the ACD mount, or maybe something else? The speedtest.net app on the ATV4 is showing > 100mbs so I don’t think it’s a wifi issue.
Thanks for any help!

install plex on ssd
https://www.youtube.com/edit?o=U&video_id=9WmISAPsJAU

Hi kfilop. Your link goes to an empty youtube playlist.