Update: The behaviour is actually more bizarre than I expected. I just recorded a game vs AI. A short summary of the key findings:
- Queue is somtimes unresponsive, even re-selecting factory won't help
- The behaviour, as said before, is more severe after some time in the game
- After trying to manipulate an unresponsive queue, somtimes the queue seems to be duplicated / copied multiple times
- When being copied, not the whole queue is copied, just parts of it
- Unresponsiveness of the queue appears to be related with units being produced. Somtimes, after a runit rolls off, I can remove or drag & drop items from the queue
- Drag & drop often works once or twice and then stops working. If so, right-clicking also stops working
Video link with some commentary: https://youtu.be/Jmohdz4ACrU
..sorry for the crappy microphone!
By looking at the behaviour of the queue being duplicated: It appears as if this might be a result of all the failed attempts of right-clicking being somehow added to the queue?!