Files app can’t load contents from DTTG

I wonder if there’s an update on this issue.

I’ve ran into some trouble. Files app shows the available folders on my db from the browse window (see first img) but when I access a folder which within DT2G contains downloaded PDFs (2nd img), only 1 from 40 PDFs is currently shown.

For background, I set up PDF Expert because I’m still experiencing the PDF markup issues described elsewhere (Apple Pencil PDF markup issue). Last week Files App could see the entire contents in that folder (a mere 66MB though part of a large db). Today Files app shows me only one file, which means I can’t access any of my material for marking up.

A strange and possibly related thing is that Files reports that the relevent folder ‘! To Read Research’ was last updated ‘Today at 08:35’ (I worked with these files all morning in DT2G so there is new data available). Another oddity is that the ‘Recents’ tab on Files App does show some PDFs from the relevant folder because they were open last week.

Is there any way to update this manually and force Files app to retrieve the contents?

I’ve noted @eboehnisch references to memory problems particularly on older machines. I’m on a 5th gen (2017) iPad so RAM may be insufficient? Then again it all worked seamlessly for me last week. I’ve killed all apps and restarted the iPad twice, to no effect.
Thank you!