Has anyone experienced a persmissions error with this (or similiar?)  I created a process builder to trigger on case creation or edit with a formula listed below.  This error "Workflow action failed to trigger flow" only occurs on creation of the case and only when the assignment rules box is checked.  I do not get the error message when testing with the system administrator profile, however any of other custom profiles error out (which makes sense that it's something permission related as the error message points out.)  Does anyone know what configuration may be able to help me?  Thanks all.  


condition:
[Case].RecordType.DeveloperName = "IT_Cases" && [Case].Case_Resolution_Description__c <> null  &&  (ISNEW() || ISCHANGED([Case].Case_Resolution_Description__c)) 

Action: 
Post to chatter what's in the Case resolution description field.  

Workflow error details:
An error occurred at element myRule_1_A1 (FlowActionCall).
You don't have permission to do this.

This report lists the elements that the flow interview executed. The report is a beta feature.
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Flow Details
Flow Name: Case_Resolution_Description_To_Chatter
Type: Workflow
Version: 1
Status: Active
Flow Interview Details
Interview Label: Case_Resolution_Description_To_Chatter-3_Case
Current User: Samuel Lau (005j000000C9LBZ)
Start time: 1/13/2017 10:56 AM
Duration: 0 seconds
How the Interview Started
Samuel Lau (005j000000C9LBZ) started the flow interview.
Some of this flow's variables were set when the interview started.
myVariable_old = null
myVariable_current = 500j000000ORKkYAAX
ASSIGNMENT: myVariable_waitStartTimeAssignment
{!myVariable_waitStartTimeVariable} Equals {!Flow.CurrentDateTime}
Result
{!myVariable_waitStartTimeVariable} = "1/13/2017 10:56 AM"
DECISION: myDecision
Executed this outcome: myRule_1
Outcome conditions: and
1. {!formula_myRule_1} (true) Equals true
Logic: All conditions must be true (AND)
POST TO CHATTER: myRule_1_A1
Inputs:
text = Resolution Description: {!myVariable_current.Case_Resolution_Description__c} (Resolution Description: Test )
type = null
subjectNameOrId = {!myVariable_current.Id} (500j000000ORKkYAAX)

Error Occurred: You don't have permission to do this.