CB dual hormone OPK false +ve?

[Derbyday]

As per the title really. I've been using the pink CB OPK since coming off bc a few months ago but this month decided to try the purple dual hormone ones. Tested cd8 and got an empty circle. Tested cd9 and got a peak (fixed smiley) with FMU. Cd9 is crazy early for me and I had no other ovulation signs so used a pink OPK that night which was -ve.

Fast forward to cd17 and I get ov signs so tested using pink OPK until I get a +ve on cd22. Pretty sure this was it for real.

I thought you couldn't get false positives on the CB OPK so what the hell happened on cd9?

I think it is possible to have two surges in a cycle but sounds like the second one is the right one! Ive heard a lot of conflicting things about the dual hormone one, I'm tryig that one this month but I usually use the pink one.