Have a look at the CO1’s plot:
Look at it’s 180º plot. See that bump between 3 and 15kHz? That is additive to the 0º. So, if you have a reflection coming 180º and if it is also out of phase with the 0º, you will comb filtering, so be careful. If it is in-phase with the 0º, you will get a boost in this region of the eq depending on the level of the 180º is.