Remote Apps lose connection to server (but work through browsers)

[stormloaded]

Server Version#: Version 1.14.1.5488 , Xpenology server (Synology DSM-6.1.3)
Player Version#: numerous (Apple/Android)

Apologies if this is in the wrong section, ive recently change broadband providers and setup the new router for port forwarding for remote access.
Static IP has been assigned to the Plex server, and ive tried with UPnP and also created a rule for 32400 to try and watch content remotely.
i can connect to the server, and see all content when remotely accessing (tethered from phone on 4G), however no content will play through native apps, everything says the connection to the server was lost after a few seconds of waiting for the content to play. (Playback has stopped because the connection to the Plex Media Server has been lost)

This only applies to native apps on the device (eg Chromebook,. Android handset, iPad app) - all those devices fail when try to watch remotely through the app, yet on the same device if i load a web browser (eg chrome) then im able to watch the content with no issues!
im confused
have tried disabling UPnP and forcing 32400 > 32400, but no change
done factory reset a couple times on the router, same issue each time.

havent got a clue why this is failing - i need to see if my Roku is also affected but am not going to my holiday home for a few more weeks to test it, but want to try and get this ironed out before we go else the kids will moan they have nothing to watch!

anyone come across this before? its weird that its ok through a web browser but fails no matter what app is in use (apple/android). This has worked fine in the past, i had a search around the forums but couldnt see anything related already raised.

thanks

[stormloaded]

thanks will have a check of those settings, though shouldnt be any performance issues will double check (turn it right down) - the server runs a decent CPU, in testing after i installed the new CPU managed 7 concurrent streams - 2 direct play, 5 transcoding [2 remote as got a couple mates to test], all played without issues, just didnt have any more test devices, and have full 4g signal but couldnt even get 1 stream started as a remote user today using the apps but no streaming issues with the browser as a remote session! bloody weird. i guess something has screwed up somewhere with this new router, its the only thing thats changed. i need to try and get the old router working with the new provider i think at this rate.
i couldnt see anything in the debug logs either, so looks like other than remotely successful at reading the library, attempting to play probably wasnt even hitting the server, its weird

will certainly try the exoplayer v2 anyway, wasnt aware of that - cheers