Inbound action Update Incident (BP) isn't updating additional comments?

[JP-ODU]

We use the baseline Update Incident (BP) Inbound Action, which is supposed to append any email body copy into the comments of the relevant incident. After a system upgrade from Quebec to San Diego, however, I've been made aware of cases where an inbound email from a user on the watchlist isn't doing this? 

The notes activities include the email received from the watchlist member, but there's no corresponding entries copying the body text into Additional comments. Looking into the received emails, themselves, in the system mailbox: I note the message "Update Incident (BP) : did not create or update incident using current." So the inbound action is failing to fire and add the body copy to additional comments? How can I further investigate and fix this?

We're using the baseline Update Incident (BP).  It runs on reply with order 100 and has no role or conditions. The script is:

gs.include('validators');

if (current.getTableName() == "incident") {
	
	var gr = current;
	
	if (email.subject.toLowerCase().indexOf("please reopen") >= 0)
		gr = new Incident().reopen(gr, email) || gr;
	
	gr.comments = "reply from: " + email.origemail + "\n\n" + email.body_text;
	
	if (gs.hasRole("itil")) {
		if (email.body.assign != undefined)
			gr.assigned_to = email.body.assign;
		
		if (email.body.priority != undefined && isNumeric(email.body.priority))
			gr.priority = email.body.priority;
	}
	
	if (gr.canWrite())
		gr.update();
}

[NMcLaren]

@Sean Addington would you be able to share the ACL rule you created/modified?

I'm interested to see if you just unlocked this one element, or essentially all 'closed' tickets can now be modified (which I don't want).

@JP-ODU - did you take out both lines, or lead the gr.update at the end of the script on it's own?

if (gr.canWrite())
		gr.update();