Problem with MSTS japan route

Ok so it's the odaku rail or something like that and I was driving a LIRR ALCO down the line towards Hakone and right before machida my diesel uncouppled from my cars and It happened all the time. So I tried a whole bunch of other diesels and made consists with the lirr coaches and found out the same thing happens in the same spot no matter which direction you are heading in. ANy one know of this issue and have a fix for it.

Probably going too fast. I've seen this happen with other locomotive/rolling stock combos. Even if you are doing Explore with the option for derails off, the couplers can still break and send your train one way and your engine the other.

but i was going 1mph with it was just making a random activitiy involving nothing but LIRR trains and was gunna post it on your site I think now how ever I will have to change the loco to the M1