Hello!
What happened here is that the back bet was matched at a higher price than the trading-out trigger intended. Judging from the figures, the back price should have been 10.0*4.4/17.6 = 2.5, yet obviously in that very moment the price jumped to 3.07 and the bet was automatically adjusted. This created an unequal P/L on the selections, so the trigger kicked in again to fix it.
I have turned off this option. See the corrected triggers attached.