@martin_pl given the huge amount of features and various mods this game has, it would require a triple-A studio to maintain it in a way where there are little or no issues on releases and updates. Even such a large studio would have issues keeping the game completely bug free.
Given the fact that we are a voluntary organization with people choosing to donate their time to work on the game, we can't act as a triple-A game studio would.
Instead we have two choices:
Release updates which may break things and do our best to fix them as we become aware of them. Of course doing our best not to break things in the first place.
Or,
Release no updates at all and leave everything as is.
I'm fairly confident it's in everyone's interest that we stay with option one and it's a part of our core mission to keep expanding on and improving the game.
@jip thank you for the work you're doing.
The coop missions were worked on quite extensively a few years ago and perhaps it's worthwhile reaching out to those contributors for help?