Dairy challenge for 11m old

Hi! I'm doing a dairy challenge on my 11m old. I've been dairy free/soy free for 7 months so my milk is clean and baby's BMs have been at baseline for quite some time. My goal is to wean within the next few months, if possible. Also need a backup if in case my supply drops. So I figured instead of the dairy ladder I would try to challenge by adding an oz (and increasing by an oz daily) of Kendamil goat formula to the breastmilk bottle. We're on day 3. Yesterday he had a mucousy poop, which he hasn't had for months. From what I gather, mucous on its own is not necessarily a fail. He is sleeping well, but has been fussier than usual. Its possible that it's teething related and I don't want to stop the dairy prematurely if that's the case. My question is should I continue to challenge with the Kendamil until it's absolutely clear that it's a fail, should I switch to an HA formula and if I do, should I wait until he's at baseline again before trying?