Connection Issues when playing Solo, that don't appear in Coop

I experience constant lags in FUT in FC26, but only when playing any of the competitive game modes (rivals, gauntlet, live events, draft) solo. I do not have these connection issues when playing Rivals, Rush or Live Events in Coop with a mate.

I usually have a ping of between 10 and 20. In solo, the ping spikes to values of 100+ about every 20 seconds, while it is mostly stable when playing Coop. It doesn’t influence my connection whether I or my mate are hosting the Coop-Lobby.

I have played about 30 games Solo and Coop each. I had these lags in every Solo game, but only in about 10% of Coop games, which makes me believe that this is not an issue that is caused by my connection, but rather a software issue.

My PS5 is connected to the internet using a LAN cable, that has not caused any issues in the past. I have crossplay turned off, and approximate location matchmaking turned on. My coop mate has the same settings. I have played around with these settings, but the connection issues remain in any case. My internet connection has a download speed of 100 Mbit/s and an upload speed of 40 Mbit/s. Furthermore, I have not experienced similar issues in FC25 and I do not experience connection issues in other games or on other devices.