I've had those file size jumps before ... Weird ! It doesn't happen often, but when it happens, it's really pervert : you can guess your file is corrupted, unless you check its size . Or if you pull vertices like you did . At least we know more about this bug now : according to your experience, it comes from an unwanted duplication of the vertices, right ? By the way, how did you get rid of it ? Did you weld the model with a low tolerance ( 0.01 or something like that ) ? litst litst.@freesbee.fr