Thank you!
I have found the issue, it was the keyword exceptions, they were added to the wrong input. I moved them to the right place: https://i.imgur.com/cZ2zWtK.png
That explains all the issues. In the case of “medications” the keyword “on” was triggered for replacement, so the keyword became “medicatis” – whihc yielded no result. With the current configuration only the whole words will be replaced.