The checksum and .mo file

or checksum calculated and stored in other place? where?
in Russian locale there is letter ё which is very similar to e.
if i edit (search and replace - ё to е) in Notepad++ .mo localisation file - why locale fallback to English?
i edit in overwrite mode - not insert. new bytes is not added to file (as far as i imagine)
but - utf8…

maybe i delete or insert more bytes when is been.

how to solve this problem?

what name of section in .mo where stored vocabulary for search purpose - in receipt-book or in V-search or in somewhere else.