@Solla-topee Good point, should have thought about that myself. The problem persisted even using the SIM-card in a phone, and using a differn SIM in the router solved the problem. So the problem is...

Since around a week or so I have a weired problem with my internet connection through a 4G SIM-card in a TL-MR6400 router. Certain websites won't load (e.g. dropbox.com, some news websites), while...