Strange things happening at a siege

[FaceLess]

I have experienced this twice now with the C'tis castle being the Last thing on the map not owned by me. The dominion tricks sounds a good idea but starvation takes a long long time if indeed has any effect. The C'tis fortress had been sieged nearly the whole game, first by Jotenheim AI and later by me (around a 100 turns I think). The earth spell did do damage every turn but that was apperently repaired before the troops kicked in. I used the Ulm siege commanders and troops to open it up but still needed a lot of troops and time. Subsequent storming was also unsuccesfull for a couple of times (and resulted in a completely restord fort with 1400 troops)before I finally broke them.