I'm not sure what's happened to cause it to drop again...

I'm not sure what's happened to cause it to drop again but it's enticed me to have another dabble. I need a refresher on ASX best execution policy however as I placed a Buy order which took out the open sell offer but then found the open order (with the residual handful outstanding) pushed down the queue later in the day.

So I went from first in queue to being pushed down the queue by later orders which executed while my (partially filled) order kept sitting in the queue. I don't understand how that can happen (newer orders getting queue priority).

Any ideas?