Ultima 4 - Can't [U]se Item in Battle

[solkitamura]

I've been playing through Ultima 4 with the enhanced version, and have encountered what seems to be a game-ending bug. While the key commands work normally in dungeon and overworld navigation, when I attempt to [U]se an item in the Battle screen my characters move randomly and I get the text "not here." As one needs to be able to [U]se items in battle to gain keys necessary to complete the game, it makes the game unwinnable.

I'm using the latest daily development build (git7584-g3aa5b2883) and have attached a save game just outside the relevant combat screen.