Conditions quantity in $SELECT()

I use $SELECT() in Architect to aggregate various data conditions into a single dimension.

I have a data table like this: id, user, userData1, userData2...

Where each user action is the %Integer ID of that action from some source. Then in expression field i use: $SELECT(userAction1:"This user action", userAction2:"That user action"...) and so on, up to 14 conditions, excluding the default placeholder 1:"Other" (which is always empty because there is a condition with 100% chance). The logic is simple: if userAction1 is not null then SELECT return "This user action" and so on. The end result is that I get a perfect measurement with all the user data labeled the way I want. (Until the sum of the conditions hits an invisible wall)

After that, if we check the dimension in the analyzer, we find that only 10 conditions fall into this dimension; the rest are missing somewhere

I checked the documentation, and there's no description of the hard limit. I asked dc ai and he said the same thing. Perhaps the hard limit is an undocumented parameter?