Yeah, I tested it at work when I got it, it was spot on. I didn’t have grease on the bolt but it did have loctite on it. Just one of those fluke things I suppose.
How long ago was that? I get my wrenches re cert'ed every year (mechanic) and often see them shift a bit. Some models shift around more than others.
Recently, a friend mechanic lent his, "Checked it when I got it... 6 years ago!" torque wrench to someone who snapped a truck cylinder head bolt with it! After the WTF's, I had him send his off to the cal lab... 35# off!