Ok, now that we found the cause you need to make sure your rules on the WIFI net are right. If you don't intend to route the devices on that network through your VPN connection, but want them to talk to devices on another local network you will need an additional rule. That rule needs to be placed above the default rule, with the source of your WIFI net, the destination will be your local network(s) and it's gateway needs to be "default". That is because currently all connections coming from your WIFI net will be routed out of your WAN gateway.
For more in-depth details you better read up on policy routing.