1) What Campaign Difficulty level did you start the game on?
2) 120 figures / battalion is High unit size. For 160 figures / battalion set to Ultra unit size in Game Options.

VH for Campaign, Easy for Battles. Didn't know battalion size was a game option. Thanks.

Originally posted by debtmars:

VH for Campaign, Easy for Battles. Didn't know battalion size was a game option. Thanks.

Oops! Missed that. Thank you.

I still have my save files for a speed-run test earlier this year. I reopened Early August end-turn and verified that I was at peace with Venice (at diplomatic standing of -62) as here:
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3035494047

Then I pressed the End Turn button and was notified that Venice DOW'ed, just as in the earlier speed run and other campaign play-throughs.

If you are not getting a DOW from Venice, I suggest doing so yourself at this point. The Papal States will join them, but you still avoid DOWs from Lucca and Tuscany. I have no recollection of ever not getting a DOW from Venice playing on VH-VH. I would not expect the Battle Difficulty to affect this - but perhaps so; it's certainly the case that lower Campaign Difficulty levels will affect AI aggressiveness, if only because the absence of their economic and recruitment buffs make their forces weaker and further away from the Player..

I believe I had to DOW Venice on the above on lower difficulties of my speed run. I was testing, on N-N and above, how fast I could get to Klagenfurt being super aggressive. On H-H difficulties I was able to sneak past the Austrians blocking the mountain passes, to get there in Early January of 1797. However on VH-VH I have been unable to get there before spring 1797.

Thanks so much for the suggestions.