Whenever I play Dark lord Soma. It softlocks the co op game with my friend. What happens is I get stuck on the screen to select a weapon after getting a set amount of kills waiting for my friend to get the same screen as a popup I presume as I can't click anything. However it never happens and once my friend levels up he selects a level up and then I can select a weapon in the gift. Then after selecting the weapon I go into the level up screen. However I end up in the level up screen where I wait for him to select a level up which he already has. And he is waiting for me to select a level up which I cannot. The only way to continue is for me to alt+f4 so he can finish the run
I am sorry, I don't have any video or something similar. But it has happened multiple times when we have tried to play normally so it seems to be fully consistent in each round. Just as a sidenote, he is the one hosting in case this makes any difference for the softlock if you try to recreate it.
The platform we use is steam