KOreader file explorer unusably slow on Boox

Hello,

I have just purchased an Onyx Boox Go Color 7, and installed KOreader on it via F-droid. I immediately duplicated the library that existed on my Kobo Clara HD (by selecting and delivering all of the books through Calibre) onto the microSD card I have plugged into the Boox. However, when I try to open, for example, my "Non-fiction" folder (2000+ books) the app freezes for 10+ minutes before entering the folder, and this doesn't seem to be a one time phenomena.

I'm mostly confused because the same set of books and directory structure functions perfectly well on my Kobo, which is less powerful. The less files within a folder the faster it seems to load, but it is always slower than it would be on my older Kobo.

Is there some background indexing process, such that these speed issues would be sorted if I left it open on my desk for a week? Or should I add the books in batches of <100, rather than all at once?

Any advice would be helpful.

Edit:
Once I've navigated to the books, actually reading them is fine, it's just the file explorer that is unusually slow.