Bulk Rename Utility

New to BRU and have 1000s of photos. For some reason after renaming photos with psd extension some of these photos show white screen or blank on Win 10 explorer after renaming - not all only a handful so far. The file can be opened and nothing is lost in the file but was thinking there might be a setting to fix this. Suggestion appreciated. TY

Hi, was their extension changed? Do they work if they are renamed back to previous name?