[0.17.65] Multiplayer lag issue

[agr1as]

Started a game with 2 of my friends. We were playing for 2.5 hours and everything was fine, then they started lagging, getting "Server is not responding" messages (I was the host). We rehosted with one of my friends being host now, and I just absolutely can't play, getting the same "Server is not responding" messages all the time.

Tried restarting my router, checking my internet connection - everything works perfectly, except for Factorio unfortunately.

I would've understood if we weren't able to play at all, but for 2 and a half hours everything was perfect and then this happens.

Is there anything else I can do to diagnose of fix this problem?