It is the direct translation of the English phrase ‘going off the rails’.
The phrase has a couple of meanings depending on the context in which it is used:
1. It is used to tell someone that they are behaving in an unacceptable way.
2. it used used to tell someone that they are lying or over exaggerating.
Byale wa seleka. O tswa mo sporong byanong. 😂😂
— somebody 🤾 (@ImmanuInk) June 2, 2018