Cleaning the battery connection seems to have worked!
They didn't look particularly bad, but they have never been cleaned. I already had one of those tools with the brushes to clean both the terminal and the post, so I just disconnected them and cleaned each one at a time. There was not real corrosion to speak of, but I cleaned both sides of the connection anyway.
Truck started up like it was new! Bonus, the 12volt.solutions remote start is working better too. For a while, the 2-way remote was only acting as a 1-way remote. I don't know if it has to do with cleaning the connectors or essentially resetting the ECU, but the 2-way remote is acting like a 2-way remote again.