this one is on me , I sequenced 2 terrain's modifications within one frame , jcl said it needs a frame to update so makes sense to wait a frame for each terrain piece to do it's updates , what is difficult however is to actually figure out that some bizarre behaviour is the result of a needed wait ,not something you would always expect .

I had a smile when i started noticing that somehow what I read in aum became true in a creepy way ,in most cases the wait seems to do magical unexplainable repairs ,for instance take my recent bug report where a wait somehow made something work wich aren't suppose to work ,and turned out to not even be a frame wait problem ,but by Jupiter how it read my mind I don't know !

the wait seems to have a much bigger importance than one would expect ,there seems to be a lot linked to what happens after one frame under the correct circumstances .

the "make game" or "fix game" button must be titled "wait"