There are probably a hundred or more posts on here about regression and housebreaking problems, so it is somewhat common, I know we went through it at about 9 mo-14 months, she seemed to be a bit rebellious and at the time, I thought she was marking over where I had some incidents of marking when I dog-sat for a friend, but I'm not so sure, Gucci is pretty dominant, so I don't think that would be exclusive to submissives/ b-types
One thing I noticed on pad training (and even outdoors) that she didn't like to poo in the same place she pee'd, I'd keep an eye on what yours is doing and where to see if maybe that is why, that quirk tends to be with some of them.
You just have to go back to basics and start housebreaking like the beginning, its no fun, but eventually they 'get' it.
It was a good 2 years before I really felt like all of the 'accidents' were over, I only know she will go in the house if she is upset that we left her here alone/ like anxiety, or if she has diarrhea and she will try to make it to the door to get out,but there has been a few times she hasn't...
Fortunately, we haven't had that runny stool problem for a while.