New lag behaviour, yay

Until now the connection to most players has worked fine - good ISP, global coturn server and in Europe, so distance isnt an issue.

Something new for me started a week ago. The game runs fine for maybe 5 to 10 minutes, until I start seeing occasional issues with everyone connected to me (connectivity screen pops-up and everyone has a countdown for a few seconds). This happens once a minute or so. After a while the whole game becomes jittery. It is like my FPS has gone down to 2 frame per second and essentially the whole game becomes unplayable.

Sound familiar to anyone?