I am saddened to say that it seems that my project just died
I had a family called "Ships". That family contained two sprites: "Fighter" and "Bomber".
Both sprites were also part of the family "Selectable Objects".
During the development process, I experimented with behaviors a little bit to see what could be achieved, so both sprites had the "RTS", "Turret" and "Line of Sight" behaviors.
When I selected my Fighter-Sprite and removed the "Turret" and "LOS" behaviors, because I didn't need them anymore, my project wouldn't run anymore.
When trying to preview it, it would tell me: "Behavior name: 'Turret' not found".
Now, I know that some might think that the problem lies in my event sheets buried somewhere, but my code is very well organized. Everything is stored and ordered into certain groups. Even deactivating all groups but "Setup", where he sets the screen resolution, would give me that error.
I tried moving families around, I tried adding the behaviors again (when adding just "Turret" but not "LOS", it would tell me he couldn't find the behavior "RTS", which is CLEARLY a bug, so I had to re-add "LOS" too).
When "Turret" and "LOS" were added again, my project would run, but all private variables for the families affected were "Read Only", meaning I could read them out in my debug console, but couldn't change them anymore, even though I checked during runtime that the correct events were triggered. This means for example:
Pick all Ships where 'status' = "Idle"
Set Ships('status') = "Roaming"
Debug.Text = Debug & "Status should have been set here"
And yes, I got the text on my debug console. However, the ships were still set to idle.
I guess there is no hope but to start from scratch now?