@AlexVP I ended up using only one WAN.
As soon as I got rid of the second WAN, OpenVPN started working correctly. Under Firewall > Rules, I added rules to both LAN interfaces so they can't access each other. For the WAN interface, I added rules & under NAT > Port Forward I mapped the WAN ports to the CCTV LAN so it works how we need it to.
I know our network is fairly simple, but if you can make it work with one WAN it'll be a lot easier to manage. If I do set up a second WAN, I'll let you know what I did to make it work.
Thanks for the tips @Gertjan. If I had added logs it would've made it a lot easier to figure out what I did wrong. I made it work with one WAN, and I'm leaving it that way unless I need to change it.