Pleco File reader issue

Hi, I got pleco on my Android Tablet. Its an older Android version but I wonder if you guys have the same issue.

When I open an PDF with pleco via the file read, connect the 'add vocabulary' with anki, it won't add words thst pleco does not know, So I can't add a phrase or a whole sentence which is pretty sad, instead Pleco errors and I got to restart it.
It adds all words pleco has in its dictionaries... however not the ones pleco doesnt know.. can you change that somehow?