I think he refers CBC jerks may cause derailment. Its really Funny when we listen people who consider themselves as experts and comment's about CBC jerk, Few hilarious sentences which i heard during my travel in TVC mail , Kaveri and Malgudi by the passengers.
1) I think the driver does not know to drive properly . He is not releasing the brake lever properly ..
2) The coupling is very loose.
3)...
more... Stupid maintenance.
4) This is an Epic one by a lady when i was onboard Kaveri express .. i think some engine is coming and dashing from behind