Every time i start making a map, i am able to edit it. After about a total of 10-20 hrs (reopening and testing map) of editing the map, i open it from the folder it was in, and an error pops up either saying "Main map file cannot be opened" or "Level data missing or invalid" i've been recently using maps w/o imported models hoping it mite help, but it doesnt. if anone knows how to fix this, plz help. (i can open it once in the Test folder, but once i shutdown reopen it to edit next time, there is an error again.