Issues with markup on iPad Pro (via Continuity/Quick Look from a Mac)

I have several PDFs on my Mac that I've been marking up on a connected iPad Pro using an Apple Pencil. Both the Mac and the iPad Pro are fully updated to most recent OS. I do this using Quick Look on the Mac via Continuity (see here).

I'm having 2 problems with this:

1. For several PDFs (but not all), once the PDF appears on my iPad screen and is ready to be marked up, the markup toolbar flashes on the screen for a split second, then disappears immediately. The most recently used markup option is still selected, so I can still use the Apple Pencil to mark it up. But without the toolbar, this makes it impossible to use , as I cannot change the option for the Apple Pencil.

2. For several PDFs (again, not all), after I'm done marking it up, everything looks fine. But then when I open the PDF later, all my markups do not appear correctly. Instead, the markups are blown up much larger than when I made them, and they appear shifted down the page by quite a bit. Therefore, the markups don't match up with the PDF's content anymore, which makes the markup feature useless.

I'm not sure if these two issues are related... It doesn't seem like they need to be related, but there does appear to be a correlation: PDFs that had issue #1 seem to then encounter issue #2. But I haven't gone back through all of them to be 100% sure.

This is very frustrating. I have spent a lot of time marking up my PDFs, and now many are useless, due to issue #2 above. Any ideas?