On my last measurement session, after setting some delay times, I visited the mic location and realized that the boom had fallen down and the mic was near the floor and not aimed at any speakers anymore.
Obviously the results you get down between a seats and not on axis of the speakers being measured is a bad thing. You may be able to tell in the picture that the rubber washer at the boom arm base is bulging. From now on, I’ll make sure the boom is tight. If it can’t be made tight, I’ll change out stands. Obviously your measurement mic might suffer damage if the mic bangs into something.
As a side note, any windscreen affects the response of a mic @ high frequencies. Unless there is a reason to use one (like you’re outdoors), don’t. In this case, my assistant put it on and I didn’t know it.