Error with O9/O11 using excel in guardian

[MyWifesBF]

Hey guys, so I'm having an error betting on Basketball markets using excel. For the placement of back bets I have the following code

=IF(AND(COUNTIF(AM7:AM107, "BACK") > 0, O11 = "", G11 > 1.29, H12 >50), "BACK", "")

So if O9 or O11 depending on the 1st or 2nd team, if O11 is empty and all other criteria is met it will place the back bet. (O9/11 being the cell that says Placing, Placed, Failed)

This is supposed to be so it doesnt double bet because if the other criteria changes then it will remove the Back text from cell L9/L11 and can write Back again and again and place more bets

But even with this in place, every blue moon it is placing multiple bets. What I have noticed is when it does place more than one bet, the status in cell O9/11 is always FAILED but it has placed lots of bets

Any ideas of how I can fix this?

Thank you