It’s good to hear that it’s lower pallet. Less risk that way, but still important. The sugar caused flaring makes me think there is a bacterial culture isolated from your immune response and exposed to the flora in your mouth, along with what you’re eating and drinking. Proteins don’t feed bacteria and yeasts, but sugars and starches do, maltose in particular, it could be ordinarily beneficial anaerobic bacteria like lactobacillus in the wrong place.
Discussion
This seems pretty likely to me. Possibly simply the types of sugars feeding the bacteria, causing the excess production of a metabolite that is toxic to the nerve.
You probably knew that most food grade citric acid is produced by feeding E.Coli certain types of sugars. I wouldn't be surprised if this is involved somewhere in it because I also suspect citric acid contributes, the combination of malts and citrates at the same time is probably optimal for the problem to be caused, which again also points towards an acid loving bacteria.
I've had this weird issue with certain foods, especially sweet ones, that yes, malt seems to be a common factor at least to some degree, that causes nerve pain in my jaw area in general, not just on the right side but on the left as well.
It is probably relevant also that when the malt has been caramelised (ie stout beer) there is no problem with this.