That problem is with OSTicket itself. It crept up a few versions back and has never been addressed. That unfortunately is the sad truth with OSTICKET. It might be free and it certainly isn’t reliable at all.
That’s what I do, and I recommend you keep a text file with a list of each file you modified when hand-translating. If you upgrade to a new version it’s much faster to open, find/replace, than it is to start from scratch each time!