Before you blame the relay have you looked at the control board? Also check the wiring from the switch to the control board, relay, batteries, etc. If the switch melted then there was a lot of current applied and even though I wouldn't rule out the relay, they are pretty durable, I would check weaker parts in the system. If there was enough current to melt the switch without blowing a fuse somewhere I would suspect a bare wire shorting to ground maybe after the switch. That could have effected the control board or other items in the circuit. If this all checks out well as you may have done it already post the relay part numbers and we can help with the search.
Steve n' Tammy with Ella Mae the "Shippet" in a 2003 Fleetwood Bounder 32' on a Ford F53 Chassis and a V-10 gasser pulling a 2020 Pacifica on a EZE Tow Dolly