In tactical battles the graphic for the catapult moves, but the actual location is not where it appears.  Some times my defenders even come out to meet the catapult at the incorrect location.

To reproduce load saved game linked, use the garrison in Ahilga to attack the "Catapult's Army" to the east.  Let the battle start, and you should see the catapult misbehave.  This has also been reported here https://forums.elementalgame.com/433513, but I didn't see any saves to help reproduce.  Hope this helps.

Debug file: https://www.dropbox.com/s/29r8qmiou0wqec7/debug.err

Save file: https://www.dropbox.com/s/18g9er41ixrtr7z/Kill%20green%20catapult.EleSav