Off taste with artisan bread in five?

Hi all. I usually make sourdough or "nearly" sourdough loaves, but I've had a weird schedule, and I couldn't make my normal whole wheat loaf, so I thought I'd give another go at artisan in 5, since I'll prob. be using that more in some rented apartments I'll be in in the next few months (won't have my normal bread equipment with me). I decided to adapt the whole wheat recipe so that I was using 2/3 whole wheat, 1/3 bread flour. I used buttermilk powder (instead of buttermilk) and honey as directed. I left the bread in the oven after it was done, with the door ajar, and got a wonderful crust that's still crisp even today.

I plan to try it again tomorrow incorporating soaked grains - don't know if it will work.

My main question: when I've tried artisan in 5 in the past, the day of my bake the bread itself tastes quite good, but there is a really strong aftertaste that lingers in my mouth for more than an hour. I've had this with several of their loaves. Does anyone else have that experience, or is it just my tastebuds? when I try it again I will put in much less yeast and let it sit out for many more hours in compensation. I hope that will get rid of the unpleasant taste. I want to reiterate that this is not a "whole wheat" unpleasant taste - I've had it with the other loaves I've made.

Sorry to maybe visit old topics, but I wanted to see if there are any new opinions out there regarding this method.

Thanks