Synopsis
I have a sub-zap that includes data validation filters before copying a Contact from HubSpot into the destination system.
One of the filters checks that the First Name and Last Name both have values.
When I step through the sub-zap it works fine.
When I step through the zap that calls it, it always goes down this path no matter what values are in First Name and Last Name.

The path has three conditions and a fallback. The one that always (erroneously) matches was originally the third path but I moved it to the second with the same result.

The only other complexity I can think to mention is that the sub-zap is called from within a loop in the main zap.

So what next? Do I believe the sub-zap test, publish both and put them live, or do I believe the zap test and spend more hours on figuring out a work-around (copy the sub-zap into the main zap and forget sub-zaps exist?).

Testing Details
In the following screenshots I have simplified it by checking just the first name against the value “x”. In the test record from HubSpot it is “Simon” so obviously they should not match.
The sub-zap returns the names from HubSpot, so I can see that it really did select “Simon” from HubSpot yet it goes down the path matching it to “x”.


Main Zap
 

Sub-Zap
 

Back to the Main Zap
Screenshot shows that the sub-zap went down the path that compares first name to “x”, yet the first name is “Simon”.