If I remember correctly the configured options gets written to openvpn config file on the filesystem but next time you make changes the webui loads default value and if you forget to reconfigure it again and apply then the incorrect value will get saved.I've encountered it for another openvpn option prior to 21.7.3
root@OPNsense:~ # cat /var/etc/openvpn/server*.conf | grep tlstls-servertls-verify "/usr/local/etc/inc/plugins.inc.d/openvpn/ovpn_auth_verify tls 'OpenVPN' 1"tls-auth /var/etc/openvpn/server1.tls-auth 0tls-servertls-verify "/usr/local/etc/inc/plugins.inc.d/openvpn/ovpn_auth_verify tls 'OpenVPN' 1"tls-auth /var/etc/openvpn/server2.tls-auth 0