Synology access interupted by DLINK ip-cam

[Todecay]

Introduction:
I have a DLINK ip-cam (not a DCS-942L) and have connected it to my Synology NAS and it works perfectly, also with the Synology surveillance app. No problem for months so I decided to buy another DLINK ip-cam, the DCS-942L

Installation went perfectly and I also got this new ip-cam up and running on my NAS within minutes.

The problem:
When I'm outside my own network I connect to my NAS with server.###.com but after about a week or so when I enter this address I'm suddenly being forwarded to the DCS-942L admin panel and can't connect to my NAS anymore.

I reinstalled the DCS-942L ip-cam and everything was OK again but after a week or so same thing happened.

I am pretty sure I used the same ip-cam network settings as my other DLINK ip-cam.

Really have no clue what can be the problem.

Anyone any ideas how to fix this? It's driving me crazy?

PS. Antwoorden kan gewoon in NL als daar voorkeur aan is.