iPad annotations in PDF unstable

I have a PDF on my MacBook. Mostly one I created myself, but that doesn't matter. Could be any PDF.

I click the PDF in Finder and use the markup handoff to open the PDF on my iPad. On the iPad I add some annotations using my Apple Pencil. When I'm done, the PDF on my Mac is updated and shows my annotations.

First problem: This works only with local files on my Mac's harddisk/SSD. With PDFs on network shares the handoff works, I can annotate the document on the iPad, but the edited file is not synced back. All annotations are lost when closing the PDF on the iPad.

Second problem: I edit a file, it is synced back, I can see my annotations on my Mac, and then I do the handoff again to the iPad to add some more annotations. Now most of the annotations, if not all, have moved positions on the PDF pages by so much that it's impossible to see where they originally belong. There is no way to edit the PDF a second time without losing context of the previous annotations.

That makes the whole feature entirely unusable. Can this be solved?