Yesterday I was playing Ultimate DOOM with an addon mega wad during the day, taking some breaks in between. Creation and loading of a savegame worked fine so far. However today when I wanted to continue, I was greeted with a "missing addon" notification in the Launcher, although no changes where made to the addon chain. This has happened to me a couple times in the past with different builds already.
First thing I notice is, that while now a notification text about "missing addons" is shown at the related game slot, at the same time the usually visible button to access the mods management dialog is unavailable. Instead the user has to find out that he is required, contrary to the regular use of the launcher, to right-click the game slot to open a context menu where the entry "Mods..." can be selected. It does not make much sense to me, that the mod management access button gets hidden, when the user gets requested by the launcher to actually go there to "fix" something.
Next thing I notice, after I had removed all invalid addon entries and re-added the same unchanged addons to the game, that I'm not able to load my savegame, due to "missing addons". So I'm looking at the modified in-game loading screen, where pressing the ALT key to ignore and continue no longer works, instead now a switch can be flipped to "ignore incompatibilities". But how to proceed from there? There is no load or continue button available, you can only cycle between the "ignore incompatibilities" and "Cancel" button.
Overall this addon incompatibility safety system has caused more headaches and trouble than it has done anything good.