Thanks for the suggestion.
I turned off the strat redeploy both in misc and in ai settings
Code:
# Force strategic redeployment if movement time is longer then X hours. Overrides default AI settings! -1 – Disable, Else time in hours
-1 #-1
Restarted the game, confirmed that nothing is being redeployed any more. It still took a few months, but eventually, shockingly, it seems to have worked. The Garrison AI finally stopped shuffling troops around, I almost couldn't believe my eyes. Was strat redeployment really the problem all along? If so, I can't quite understand why. I thought it was just a tool for getting divisions to their destination faster, not something that in itself tells the AI where to put its troops. Also, obviously i don't want to completely disable strat redeployment as it's a very useful tool, but now i'm afraid to enable it again. I'll test out various values, but is there a reason why you think that, say, 10% would be a safe value, but 40% isn't?
Btw, when the AI is endlessly shuffling troops, it's not just a minor nuisance, it has all kinds of consequences. From increased supply consumption, to ungarrisonned beaches, and completely broken invasion AI. The reason I even started looking deeper into this issue is that I noticed that the invasion AI was completely incapable of doing anything, i.e. Italy could not even invade Albania. Turns out the reason was that the troops were constantly getting shuffled and transported around so the invasion AI could not get either the troops or the transports needed to launch the invasion. When the troops are stationary, the invasion AI also works without problems.