Sounds like some object lists are overflowing. I don't know, is there a limit to the number of teleporters on a map? UN:I doesn't check limits (like how it's possible to place over 48 towns using ERM) and WoG code tends to not work properly with lists. What objects do you place with ERM? Also if you manually change type/subtype of a tile, then from and to what?
Restoring control word, you can do this no later than next !?GM1, otherwise it may cause problems for objects with limits.