It would not surprise me if those were counterfeit. I had several parts that I bought in an NTE package, used them, and they failed immediately. I thought I was missing something, so I sent the board to Chris Hibler. He showed me that the failed part was "blacktopped", and that the part I was using would test OK on a bench, but then would fail under actual conditions.

Look closely at the markings, and see if there's evidence of paint strokes covering the original stamping. Yes, I believe there are people out there who go through the trouble to make these counterfeit. Also, since I've been burned twice, I only get my parts from GPE if possible.

After reading some stuff I've always been pretty hesitant to buy stuff off ebay. They always have those hard to find caps though.
So far I haven't had any issues at least known issues. I usually test everything before installing, but like you said putting some stuff under a load for a prolonged period of time can be different from bench testing.

Seems like a counterfeiter will do this to any item, if there is any chance to make a profit off of it, regardless of how slim the margins are.

Maybe it's a bad batch...why would you counterfeit a cheap and readily available transistor? Making it look like a Tip102 is like 90% of the work already.

Strangely enough - they counterfeit the cheap stuff as often as the pricey stuff. They often take lesser parts and pass them off as the pricier parts. But in this case - the lesser part would be a TIP120 which is pretty much the lowest end of TO-220 darlington transistors....which should also work. My guess.... bad batch.

But a batch from Digikey? That one is rather difficult to believe (not saying I don't believe, just that this would be a really rare occurrence from a franchised seller). Could have been mismarked by the manufacturer.

For something interesting - search for 'counterfeit eggs'.
An incredible amount of time goes into making one yet they still do this. I suppose they consider their labor 'free' and don't care how long it takes.