How does this happen?

Hi
Very difficult to say without further info like the trigger logs.

From what I can piece together:
Scheduled off time was 15:55 (searched for selection name in results)
Bet was placed at 15:52
Please can you confirm the actual off time as 15:50?
If not, I am assuming the back bet was placed quite a few minutes before the actual off. If the best back price at the time of the bet was 1.64 (r_ticks(back_price,-1)
what was the best lay price? i.e. was there a big spread?
What I am suggesting is that the back bet may have been placed far too early.

Also, why not add a condition to check current back_price is not too far away from projected SP price at the time of backing:
near_sp
far_sp
 

Hi
I was thinking of between a min and max to be safe. It depends how tight you want the conditions.
and selection’s back price is greater than r_ticks(near_sp,-5)
and selection’s back price is less than r_ticks(near_sp,5)
and selections trigger expression g_ticks(back_price,lay_price) is less than 10
and market’s minutes before the off is less than 2

You can adjust the numbers as you want, but this should stop that happening again.

Edit:
Obviously the above conditions apply to before the off, so you would have another condition block for in-play:
OR
market's status is in-play
(here your price formula kicks in)