Found the problem and solution! For context: I connected the tplink router to my FritzBox router in order to extend the network and use the "Router Mode". When devices connect to a router, they get...

@woozle thank you for the response and sorry for my late reply. It looks like disabling SPI did potentially fix the issue. But what could be the reason for it? // EDIT: It actually didn't help. The...

@woozle yes. Sorry forgot to add that. Only with one phone it doesn't work since it seems like it most likely has it enabled on default or we just don't know how to disable it.

Hello, I have the problem that suddenly some devices aren't having an internet connection. They can connect to the router (so it can't be blacklist) but just cannot connect to the internet and their...