I currently have a teltonika rut956 connected to a plc, but the plc has a static ip-address of 192.168.1.10/24 (which i cant change since I am connecting remotely)
You need to add a second address to the lan interface using ssh or CLI:
ip -4 addr add 192.168.1.1/24 dev br-lan
and delete your static route. As you connect remotely I suppose you also need to add 192.168.1.0/24 to the Allowed IPs / right subnet / … to your VPN config.