Buy sell volume

I Have noticed over the past month or so that in the buy and sell sides of the Market Depth sometimes there will be sellers and buyers at the same price .
ive never seen this on other stocks albeit i only trade Westpac Shares
only thin i can think of is the seller and buyer are the same person
i use etrade and it wont let me do that
anyone know the answer
with all the current good news plus plenty more news to come , i see only upside ATM
good luck to all those patient holders