I would suspect pancreas issues for sure so definitely rule that out.

I would also suspect a new reaction to a food ingredient. My senior dog developed a rice allergy at about age 12 and any rice would give him diarrhea for days. We had to stop eating it ourselves because of the kids even dropped a few grains, he would eat it and get sick. Check what the main grain is in your dog food and try one that doesn’t contain it. There are some high end dog food blends that avoid rice/corn that you might buy a small bag of and try. Eg some have quinoa as their grain.