No
Tried. No change
Great idea 
I´ve got another SmartTV with a different OS (LG with webOS) and a different Plex Client.
This one has exactly the same behaviour as the first TV (Philips with Android):
Access to Media on Synology DS is possible via simpleshare/DLNA, but PLEX on DS is not available
I also connected the second TV to the other switch. Same behaviour.
Interesting is, that the problem seems to be dynamic:
PLEX Server on DS was available on the second TV a few days ago via WiFI. Now, even WIFI does not work, although there was no change. Also, PLAX was no more available on the PC although it worked well there a few hours ago.
I found out that there are lots of Plex Media Server processes waiting (“schläft”) on Diskstation. See attachment. I stopped PLEX and started again, and now PLEX is available again at least on the PC. On both TV sets it is still not available.
