Well, truth be told, I've never yet once used TL++, but for trying how about making the 'img' and, I guess, 'audio' folders and/or their contents read-only? I guess the TL process then might throw an error? Hmm.
Or you could try making a backup of the originals, and swapping back the 'img' folder, for a try? (and maybe the 'audio', if that gives problems)
Could it have something to do with -only- translating those filenames that happen to have Japanese characters in them?
Damn sure it's not normal. Unless those referenced filenames also get a TL in the script files, which I highly doubt. Probably should be ...
...
Wait. I misunderstood. So, in fact, what's actually been happening is that the software effes up the scripts by TLing the filenames they are pointing to, while in the 'img' folder you still have the original filenames - hence the error.
There really must be a checkbox to (un)check or something that would keep it from rampaging the scripts... At least I'd assume so.