IP Fragmentation

Lately when I 'test' my wifi on the PS4, it gives me a message in the bottom of the screen which is about IP Fragmentation and that something is not supported by the router. (I always get this message when it is determining my NAT-Type) I didn't change anything with my router and nor did anyway in my home. Do you have this problem as well or the solution for me? (My wifi is very bad so I'm going to buy a WiFi Range Extender, more info on that over here)

Edit: Just tested my WiFi 1 minute ago and now I don't get that message anymore, but please still reply!