Unwanted diacritics when editing text

I've scanned a lengthy document which is mostly English but with a lot of Czech names in it. I'm amazed how accurate the OCR is. Mostly there are only missing letters (particularly 'N' and 's'), but also cases it inserted space or the OCR failed, and I want to re-type a word here and there.

However sometimes when I type 's' it immediately changes to 'š'. Or typing 'e' becomes 'é', or 'a' becomes 'á'. Copy paste has same issue.

I'm able to insert missing diacritics in Czech words/names, but I cannot seem to remove the ones that Acrobat has 'decided' belong there. I was able to fix one of these somehow (maybe saving document and restarting?) but it keeps happening randomly.

I've got a lot more editing to do so so far I am just noting where this happens so I can come back and try to fix them later.

Just wondering if anyone has seen this or has suggestions.