I don't know if it rare. However, I suspect it occurs more often than we might think. Many people simply have faith that they do not or cannot contain a trigger.
I pinpoint most problem foods the same way. When I become unstable I immediately drop back to my stable diet. This includes removing all supplements and other non-food items. Once I am stable I introduce the additional things I was consuming one a time. Within a couple of weeks I can usually figure out which things are giving me gas, bloating and usually D.
I do use beano - which of course is a digestive enzyme. The digestive enzymes I have problems with are the multiple enzymes in one tablet/capsule. The enzyme in beano is derived from aspergillus and it is easily purified. However, I believe that sometimes enzymes such as bromelain and papian derived from pineapple and papaya are not isolated and purified. Rather ground dried fruit that contains enough of the active enyzme is used in the preparation. The dried friuts contain mostly IF. In addition fillers such as microcrystalline cellulose, an IF, are added.
Personally, I believe it is important establish a base diet that contains no supplements which you can use when problems arise. My base diet is very simple. It consists of oatmeal, grilled chicken breast, white rice and boiled carrots. When I dropped back to this diet I find that bloating, gas and D usually stop with 24-48 hours.
Good luck
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS