msaccess laccdb lock file on network share

Question

I have a simple access database file that works perfectly fine on a local drive in a local folder.  If I share that exact same folder, then map that folder on the same computer, the laccdb lock file isn't cleared when I close the database.

The database itself doesn't seem to matter.  I created a new database with just one table and the same problem occurs:

1. create new access database on C:\localfolder
2. access works fine.  close access, the laccdb file deletes
3. create a share of c:\localfolder, then map Z:\ to \computername\localfolder
4. open access database, close access database.  laccdb lock file does not delete

the share settings are correct.  "everyone" has read/write

additional info:  if I go to a different computer and map a drive to that "bad" computer I can open the access database fine, and the lock file correctly disappears when I close it.  If I go back to the "bad" computer and map a drive to the "good" computer and open an access database then close it, the lock file doesn't delete.

Also on a good computer I can open the lock file in notepad and see info on who has it locked (me), but on the "bad" computer, it creates the lock file but it doesn't write any data to it... almost like it thinks it doesn't have write access to the file, or delete access... but it does.  it absolutely does. as soon as access closes, I can open explorer and delete the file myself.

I seriously as a loss.  This machine has worked perfectly fine with access database lock files for 4 years.  Suddenly today it won't work anymore.  No updates have been installed and there's nothing to roll back to in a restore.