Can anyone help me with STK repricing software?

How do you stop STK from doing this, or maybe it’s Amazon? For example, the lowest price is £12.99, and STK is set to match Prime offers but not non-Prime offers. However, it keeps lowering the price to £9.99.

I keep setting it back to £12.99 to match, but again, it drops back down to £9.99.

Why is this happening? I’m pretty sure it was doing this before my friend started using STK, but I’m not certain. It’s not my account; I’m just trying to help them.

Thanks!

Check if it makes the same profit at both prices by entering both prices into STK. This happens in this case.