VPN blocking VPN connections

Slightly confusing, and not necessarily directly piracy-related. I run OpenVPN on my Netgear router that allows me to connect to devices on my home network while I am away from home. It works great for most devices, but I cannot connect to any devices that are running Mullvad VPN. Disabling Mullvad on those devices allows me to connect. Also, if I SSH into a device that does not run Mullvad, I can use that SSH session to then communicate with those Mullvad devices. Any ideas?