Thanks for your time in advance. Sorry for the inconvenience. Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others." and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[Document library columns are missing after performing a move action for a document]
Issue Symptom:
After moving a document, the DESTINATION library metadata columns property is empty but the missing source columns no longer shows in the form.
Solution:
This is a known issue in the sharepoint currently. We could only create a new document library and upload the files again. It's inconvenience for extensive document and will lose version history. It is highly recommended that you can raise a ticket on customers’ feedback to report the issue.
You could click the "Accept Answer" button for this summary to close this thread, and this can make it easier for other community member's to see the useful information when reading this thread. Thanks for your understanding!