Try to start regedit, find HKEY_Current_USER\Software\Microsoft\Windows\CurrentVersion\UFH\SHC select all entries under that key and delete them.
This is ONLY "Start Menu Cache" and should not change anything, it will be rebuilt (with correct numbers) on next logon.
After that you will have quick logons again for a while.
You could make a .reg file or policy for that but that needs to be run "on logout", those entries are useful (when they are correct).