SynPUF Descendants Issue

I’m running into an issue with certain types of cohorts in ATLAS, not sure if this is an implementation issue. The following two cohorts are only one example of this occurrence. I saw the same problem with different conditions and different drugs.

Cohort 1:
Entry event: condition occurrence of hypothyroidism (140673 and all descendants)
Inclusion criteria: drug exposure of levothyroxine (1501700 and all descendants)
SynPUF record count: 0

Cohort 2:
Entry event: condition occurrence of hypothyroidism (140673 and all descendants)
Inclusion criteria: drug exposure of levothyroxine (40169766 only)
SynPUF record count: ~6,000

The strange thing is, the levothyroxine concept 40169766 is a descendant of 1501700, so I would expect the record count in Cohort 1 to be at least the same as Cohort 2, if not higher. When run against a different database, this does occur (Cohort 1 having a higher record count than Cohort 2). Any advice would be greatly appreciated.