Disappearing Master Page overrides

In a vocal score layout of an opera arrangement I’m working on, I’ve created a master page without any header except a page number, as well as a slightly higher music frame for use at the beginning of new movements (i.e. new flows) and I’ve applied master page overrides in the appropriate places. For some reason, these overrides keep disappearing, but the pattern in which this occurs, i.e. some might remain while others disappear, and the action which causes it is unclear to me. I know that they can disappear when I create new flows but they sometimes also disappear if I change the layout and then try to move or delete a page override. Is there documentation about the conditions under which Dorico removes master page overrides?

You mean a master page change, right? Dorico won’t ever remove these on its own.

Yes, sorry, I did mean masterd page change. I didn’t think Dorico would remove these on its own and I just realised that it’s very possible that I may have in my haste inadvertently selected remove all master page changes instead of just the local one. My apologies!