Just went through a bad transfer switch problem on a Xantrex Freedom SW2000. I called their customer service number and got a tech. He started off with all the reasons it would not be covered and I got upset. However, he did make the point that he needed the purchase date/information to go further. My wife was at home and gathered the information and then called him. With the information he agreed that the inverter was still under warranty but there was no coverage for a "welded" transfer switch. I had asked if we could take it to a local repair shop and order any needed parts from Xantrex. He said that they did not sell parts to anyone. So... we agreed to ship the inverter to their repair facility taking the risk that if it was the feared welded switch that we would have to pay a $250 bench charge to diagnose . A couple of days later we got the word that the switch was not the problem and the repairs were covered. Apparently the problem was too severe to fix and a newer model inverter has been shipped and should be here Friday.
Now to your problem. The older inverters are not under the same "no parts'" rules and I think you will be able to find a repair shop who can replace the transfer switch. I had an earlier model Heart Interface inverter and a repair shop in western Ohio who mostly does installs in RV's took a shot at fixing it. Unfortunately it was not repairable because a faulty circuit board was no longer available.
Hope that helps.