OpenVPN won't block external DNS

[SteveMason]

Running version 2.4.3_1

Under VPN > OpenVPN > Client Export, I selected the following option :

Block Outside DNS Block access to DNS servers except across OpenVPN while connected, forcing clients to use only VPN DNS servers.
Requires Windows 10 and OpenVPN 2.3.9 or later. Only Windows 10 is prone to DNS leakage in this way, other clients will ignore the option as they are not affected.

However, when I run the client on my Windows10 PC
a) Windows attempts to use its "normal" dns servers, whether manually assigned or via dhcp.
b) External dns queries are not blocked.

OpenVPN is connected and I get the following from cli -
C:\Users>nslookup
Default Server: dns.quad9.net
Address: 9.9.9.9

www.google.com
Server: dns.quad9.net
Address: 9.9.9.9

Non-authoritative answer:
Name: www.google.com
Addresses: 2a00:1450:4009:810::2004
216.58.206.100

[SteveMason]

Must've been legacy config or some such as the uninstaller doesn't clear down old files.

Uninstall, manual deletion of old files from c:\Program Files\OpenVPN and a full reboot before reinstall seems to have done the trick.

This can be closed but uninstaller needs work ;)