RasPi 3B+ does not run stable

I had exactly the same problem for over a year now, and only two weeks ago (after having exchanged / tried almost everything) seem to have solved it. See here for what I tried: Raspberry Pi 2 loses ethernet connection - #26 by Cplant . Let me know if this helps. Error logs would be helpful as well. Spoiler: It now only seems to run smoothly after having replaced the router (acting as an ethernet switch / probably a random incompatibility).