What Gary said.
I was typing a response just before he posted, so I'll add my 2 cents anyway:
Here's a link that provides some service manuals for various RV refrigerators. If you post your Norcold model number then maybe others will be able to offer some advice for that specific model or general information related to your problem.
http://bryantrv.com/docs.html
In my opinion, it appears from your problem description that the LP flow to the burner is inadequate or compromised or the burner is not burning the LP efficiently. There is a 12 Volt solenoid that opens/closes the LP gas flow to the burner. It may not be opening fully and is restricting flow, but I would have thought your "service guy" would have checked that prior to replacing the baffle. With the LP burner showing flame, tap on the solenoid with a screwdriver and see if there is a change in the burner flame.
The other possible issue is the burner orifice/tube. If restricted due to debris there will be an inadequate flame resulting in lower heat causing poor cooler unit performance.
If you haven't cleaned this item then do so. The last thing I can think of is inadequate LP pressure from your LP system, but that's pretty rare.
