So this is an owner financed deal and no real estate professionals were involved? Who wrote the purchase agreement and what does it say? If the buyer put down cash without a proper agreement he might be SOL, but check state law - it might be written in.It will not pass for an FHA mortguage, and they agreed to do 20% down which completely straps them from any cash.
It may make a lot of sense. They may have been forced to continue the old policy via state law. The previous owner might have had a better Lexus / Nexus insurance score than your friend. The insurance company may not have interest in writing any new policies of this type, there under no obligation.The current insurance company has the house fully insured, and yet that said company will not write any policy for another buyer. That does not make any sense.
This is the obvious solution to move things along. Everyone gets what they need. If the buyer does not have the cash the seller will need to lower the down payment. If they don't the lawyers get to make money.The sellers estate people should grant a temporary waiver/hold harmless agreement to allow an electrician to replace the panel.