I can save documents from Writer, but every time I export to a PDF, the export works, but at exiting, Writer crashes. Starting Writer, it does a recovery of several ODT documents, not the only ODT being edited.
I scrubbed out all of LibreOffice, re-installed it, thinking debris from an earlier version was somehow corrupting the Writer. No difference.
I use a PC laptop with Win10, fully patched.
It sounds as if you might have some lock files hanging around. There shouldn’t be any when LO is closed, see Preventing data disaster - The Document Foundation Wiki
Does LO crash in Safe Mode (Help > Restart in Safe Mode > Continue in Safe Mode) after creating the pdf? See Resolving corruption in LibreOffice user profile - The Document Foundation Wiki. Generally corruption shows in the user folder, not the program folder, and the user folder remains during uninstalling.
At least for me, the solution was to install 7.2.5.2 - end of crashes.
Regarding lock files, I don’t think there were any leftovers unless they resided elsewhere, and not in with the folder containing the documents being edited.
It’s also remotely possible that I opened 2-3 related documents, and one of them did some sort of cleanup. My concentration was on being able to do the exports without crashing, and possibly demolishing the entire project. When 7.2.5.2 did the export as it should, I called the issue fixed, and went back to writing The Great American Novel. (as if!)