Masks are cleared when doing project configuration

Hello I don't know if this is a bug or not but I want to ask on this.  So I make a change to project configuration as just had to fix up one small island i mean everything is fine but when I go to put it in, it has it where it deletes all the data on my mask as in the selection parts I have and to add these aren't the island I move or so. To add some still stay in. Is this something it normal does as in delete the mask data so it black or white again or is this something else.