Sometimes a flash of voltage can interfere with polarity. Don't ask me to explain, but a way back a friend bought an MGB with the factory electric fan. It overheated, and it turned out that the fan was spinning the wrong way. It was a foolproof connection and connected right, and yet the fan was reversed. The dealer could not explain this. I think a replacement fan fixed it, can't remember now.
I would suspect the jump starting. Modern ECUs are very sensitive to voltage spikes, and why relays now have diode protection.
