Had the same bug twice now.
Was playing with a mate in 2v2 premade. game crashed at the end. after rejoining the forge, we couldn't invite each other because "we were already in a party". We werent. Then when we tried to open a game this errormessage occured.
Not sure if the already in a party is necessary for this bug. As stated above it seemed to happen in a soloscenario aswell.
Both error messages occured as above.