Hi!
I have an automation rule that sums up the Original Estimate and Remaining Estimate values of issues to their Parent.

I am updating Original Estimate field with: {{#=}}{{lookupIssues.original estimate.sum}} / 60{{/}}m
and Remaining Estimate field with: {{#=}}{{lookupIssues.remaining estimate.sum}} / 60{{/}}m
However, I am getting the following error when the rule runs:

What is also strange to me, is that the rule doesn't always fail. In the follwoing image I show the Audit Log of two executions of this same rule, with the same Associated Item and Branch rule/related issues:
