The registry setting appears fine. We may have to run a ProcMon trace to see if there are references to that volume in the registry. Meanwhile, you may try turning on system protection for that volume, click Apply, and disable system protection, click Apply/OK, to see if that makes the item disappear from the listing.
If that doesn't help, download Process Monitor. Right-click Start, click Run. Type sysdm.cpl and click OK. Now, open Process Monitor and begin tracing. Switch to the System Properties dialog and select the "System Protection" tab. Now, switch to Process Monitor and stop the trace. Save the output to a PML file (All events). Zip the log and upload it to your OneDrive.