How long did you wait after the upload? And is it just the Plex server that’s unreachable, or the whole device?
Uploading may trigger processes like cataloging and downloading of metadata and that sort of stuff, which can be very processor consuming. You might need to wait until it’s finished doing stuff before things become responsive again.
I’ve had similar experiences with other services on my WD NAS, due to the low power of their processors (as that kind of thing isn’t really what they’re designed for). To be honest I didn’t even try Plex for that reason - mine runs on a seperate Raspberry Pi3 instead and works fine there. Just leaving the NAS to sling files around…
There I can’t help unfortunately. I tried it, saw how useless it was on the hardware (especially CPU) that the NAS offers and moved my home Plex server onto a Raspberry Pi instead where it has remained ever since.
@gibbylinks Based on your description, there could be an issue with the Plex Index or DB.
Try these steps
Ensure that you have a copy of the content inside of the Plex Folder on another physical device
Disable Plex
Rename the Plex folder to PlexOld or something
Power OFF the MCH (not reboot)
Wait a few minutes
Power ON the MCH
Enable Plex and wait
Verify that a new Plex folder was created when Plex goes into Enabled Mode
Go through the Plex setup process
If all is OK, you’ll need to copy & paste or drag and drop the content into the new Plex Folders, but you may run into the same issue. In this case, Plex on MCH already has debugging enabled and sends the logs to Plex dev team (these logs do not come to WD)