Since I switched from Netgear ORBI to TP-Link BE85 I constantly run into problem reaching servers. "Can't connect to server x" pops up all the time. After reloading once or twice I normally get a connection. I have changed DNS to use Google's servers on 8.8.8.8. Next time I look it has changed to address from my Internet provider. 

I have run nslookup with no issues and I have tested my Internet speed which allways are close to 500 Mbps in both directions.

Even streaming is affected. All of a sudden the image is frozen and or the image quality is severely bad. Sometimes I even get a warning about network errors.

I have tried with different browser bud that didn't help.

If I connect my Mac directly to the fiber modem I have no issues what so ever. It's clearly a router problem as I see it.