Can't delete a file at a time

[iiz]

When I try to delete a file from nav or ‘More options’ menu, I often see the file disappears momentarily and soon comes back.
If files are sorted in order of modified time, the file moves to the first position.
In addition, I can find the file is duplicated in the trash folder (system trash or .trash).
This happens not always, but frequently (40%~60%, I think).
Trying to delete the same file again seems to succeed. I haven’t seen it fails two times in a row.

I thought dropbox caused this, but after I moved my vault outside of dropbox (now it’s standalone), it continues.

I don’t know why this happens. Any idea or information?
※ OS is Windows 10.

[rigmarole]

Are you using any other sync/backup services or Obsidian Sync?

[iiz]

Thank you for your response.

Actually, I use Obsidian Sync now. But I’ve seen this behavior before I began to use Sync.

1. copy the vault folder to outside of dropbox
2. delete the .obsidian folder
3. assign the copied folder as a new vault with safe mode on
   Even in above new vault, I can see the same behavior.

I haven’t installed other backup services.
I use onedrive and iCloud drive, but no vault is in them.

I don’t know it’s related, but:
I made my vault not from scratch. I copied it from other note-taking app (simple folders and plain .txt files) and renamed from .txt to .md.
Therefore it may not follow obsidian’s rule of file naming.