Sounds like the same issue as has been reported Plex win10 client apps dropping connection to server on different pc's
I was about to open a new post on this as well, and found that one. Just thought I would let you know it looks like they are aware.
They advised they are aware on this post PLEX Player - BUG (1.28.0.1681-cc6e807c) - #4 by OttoKerner
