Does this only happen when using the context menu, or is there another way to trigger the crash?

Instead of moving the last page down you can move the first page up, if the document contains at least two pages. It seems, that moving a page beyond the valid page range, causes the crash.

I don't know how to move a page without using the context menu of the thumbnails in the sidebar.

Do you need an error log? Or something like the output of "strace xournalpp"?

By the way: after a few tests I can trigger a crash, by inserting an image in an empty document:

1. Select the icon for an image.
2. Touch the page with the pen to set the position of the picture. Instantly xournalpp crashes.

Thanks for the info, the bug should be pretty simple to fix (disable the move down option on the last page / move up option on the first page).

This second crash is unrelated; please post another issue with crash logs and input debugging logs attached.