The issue seems to be related to you converting person IDs to strings when checking if a person has parents. In previous lines you converted both sides to strings, but in the section producing errors you only converted one side.
The conversion to strings is quite intriguing as IDs will be equal regardless of being a mix of integers and floats, thus the string conversion appears to simply be an inefficient source of errors. Probably leftovers from an early version of Strive.
Viewing post in Aric's Expansion Rebred
I tried ignoring the string conversion at first when I ran it and that produced faaar more errors, but I agree that it seems inefficient. IDs are only ever integers, so I don't see the point in the conversion. But I went back to try to convert all of the called ids into strings and missed some in that really tedious block of code (that mostly works!).
Corrected all of the ID string conversions I could find. They are fixed in v.07. The other issue I'm assuming must be from the original error but am unsure. That may involve more investigation.