Moonreader Pro - unable to edit notes on pdf?

[fibbling]

Hi all,
I've been using Moonreader Pro for years and often add notes to sections of text. Today I noticed that I am no longer able to edit notes on pdfs (epubs are still working fine). Usually I tap on the note and a blinking cursor appears, ready to edit the text. Now when I tap I only have the option to delete the whole note or create another (from scratch) on top.
Since I haven't done this for months I cannot tell exactly when this function disappeared. But now I'm starting to wonder if perhaps this function was always limited for pdf files and, by pure chance, this is actually my first time ever attempting to modify a pdf note. This seems unlikely though, given my daily use of this app for years with hundreds of pdfs.
The fact that I also bought a new Android tablet a couple of months ago further complicates my troubleshooting.
Can anyone else confirm if they are experiencing this or have I just never discovered this limitation until now..
Thanks in advance,
Fibbling