As is mentioned in the OP, he already tried that.

Flipped animated tiles will only cause access violations if they have Trigger Scenery, Destruct Scenery, Buttstomp Scenery, or Collapse Scenery events on them.

Most (all?) events placed on the far right side of a level are ignored by the game - this is why that blue spring doesn't show up. The same applies to the bottom of the level. Just increase the level's width by 1 and add a wall there.

As for access violations, those can happen for a lot of different reasons. If you're using 1.23 to play the level and the number of animated tiles plus the number of tiles in the tileset add up to more than 1024, bad stuff will happen, potentially including access violations. In TSF, you can have up to 4096.

If you upload the level to a file hosting site and post the link here, someone can fix the level for you.