I have red in the discussion forums of VPN services, such as Private Internet Access, that torrent clients should have certain features disabled to ensure security. For example disable "UPnP Port Mapping" and "Nat PMP Port Mapping". To my knowledge these are techniques to get around NAT which interferes with uploading files. Why would these be threats to the VPNs security/anonymity?
UPnP and NAT-PMP are security risks and should be left disabled. They won't affect port forwarding on the VPN.
You should disable UPnP and NAT-PMP, it's not used with the VPN but could leak your IP.
TL;DR how is UPnP or NAT PMP port mapping a threat to the VPN connection?