it went like this

Notice

The mod Renai Transportation (2.2.6) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Renai Transportation::on_entity_damaged (ID 118)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__RenaiTransportation/script/event/entity_damaged.lua:370: in function
<RenaiTransportation/script/event/entity_damaged.lua:38>

i have automatic steam game recording on so i can show a clip if you add me on discord (user: @pixelatedlevis) and the error image
this happened when: i was testing where to put my bounce pad so my train would land on the tracks and not after and when i though i got the perfect location and connected my magnetic bounce pad when the train went off the bounce pad right at that tick it gave me the error

That's odd, something must have either prevented one of the magnetic rail panels to not spawn or get deleted. They're just for visuals so I can add some checks to make it just skip that part of the code if one of those things happens.