This is driving me mental!! I am on Trailhead trying to complete "Automating Processes with the Lightning Process Builder" and I am getting an error in Trailhead when i check the challenge:
"Challenge not yet complete... here's what's wrong: 
An update to an account record failed to update the mailing address fields of all child contact records. Make sure that the process is correct and that it is activated."

I have checked the debug log and it comes up with Fatal Error "System.AssertException: Assertion Failed":


However if I test the process myself it works. Somebody in another thread suggested ordering the fields as per the challange lists them but this didnt work either.

Anybody else came accross this? I have spent too long trying to fix it.