My patientsendpayments seems to crash every time someone actually tries to initiate a transaction.
First I assumed there might have been some communication problem, but now this has happend two times in a row making that reason unlikely.
I had the same issue some time ago - the short answer is that the JoinMarket protocol requires you to have the target address of a join in your wallet. I. e., patientsendpayment only works if you send to yourself, and then only if you import the target address into your JoinMarket wallet. I think there is some incentive to change the protocol to make it work as originally envisioned, but I don't think that actual work is already done on that.
In my case, this was not much of an issue, since I wanted to use that for internal wallet restructuring and sent to myself. Importing the target address' private key into JoinMarket made it work. Not sure if that is an option for you, though.