> you crash your car (FSD problem) -> Tesla says "not our fault, we're not paying" -> you sue Tesla -> court decides

That's only if you sent Tesla a written notice within 30 days of purchasing that you wished to opt out of the binding arbitration clause in the purchase agreement you had to agree to to get the car.

Maybe it's me, but I think in the worse case scenario (criminal liability), a jury will be more sympathetic to a person (acting in good faith) that had an issue because of the car manufacturer's provided system than they would to a person who installed a DIY/open source self-driving system.

And I say this as someone who considered trying out the project.