Autolaunched flow stopped sending fault emails when triggered via Process Builder

Question

I have a Process in Process Builder that triggers an autolaunched Flow and passes it a Record id.

Normally, when the Flow triggered by the Process fails, I would receive two emails:

1. One from the process builder, with a generic "An error occurred when executing a flow interview."
2. Another from the flow in question, with a detailed execution path and a precise reason for failure

However, I suddenly stopped receiving the second email - I only get a generic info from process builder, which makes debugging really difficult.

Any ideas would be appreciated.

Answer 1

After four weeks of back and forth with Salesforce support, I can confirm the issue is in fact a known Salesforce bug to be resolved with Winter '19 Critical Update called: "Check for Null Record Variables or Null Values of Lookup Relationship Fields in Process and Flow Formulas".

The critical update was already available in our Sandbox instance. After activating it, the issue is gone and fault emails work as expected.

Here is the official description of the problem: https://releasenotes.docs.salesforce.com/en-us/spring19/release-notes/rn_forcecom_flow_cruc_formula.htm

The only workaround suggested by SFDC support was to create fault lines at every step of the autolaunched flow and send emails manually.