I have had the page turn problem a lot on the Mini. Doesn't have an SD card. It actually seems worse since the update so I am hoping it is a firmware problem that will be fixed.
I don't put pdfs on, but a quick suggestion is to put a pdf on the main memory and see if it behaves any better.
I read in a Kobo review that fragmentation can cause slowdowns on SD card, but seems unlikely in your case.
Helen
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