It depends on the inductance of the cable, it sounds like it could have a lot of inductance potentially, -that can cause an overvoltage ring at the first application of power. I would put a tvs at the converter end, make it as high voltage rated as you can, so it doesn’t usually conduct…and remember the tolerance on the breakover voltage.
10uF sounds a bit measly, can you spare some more?…and just to damp out vin ringing I’d put a RC series network across the input too…….hopefully you can fix r and c by scope and see, but start with say 1uF and 2 ohms, say.
I’d also put a diode across the input, just in case, to stop severe ringing causing the input to go reverse polarity…….obviously not a giant diode as most of the time it will not be conducting.
MPS2451 is max 36v at input so make the tvs stop it ever going above 36v, but not too near the 12v of the supply
MPS2451
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Hopefully the little dcdc’s have some ceramic capacitors as close as possible to them, (if not put some there) so that the nasty high frequency harmonics don’t traverse a big loop…or else those long leads might become unwanted antennae