Loose gas keys are extremely common on Model 1 Sales. I'd check that first. Next cuprit could be misaligned FSB/GasBlock.
I've handled 2, and both of them came loose - out of the box. They looked tight, but it took about zero pressure with an allen key to loosen them. Not exactly what you would call 35-40 inch pounds.
Also the staking isn't really staking. They are just scratches on the key in my opinion. They do nothing to prevent the screws from coming loose. All they do at most is keep them captive. That won't matter since the rifle will not function at that point.
Model 1 isn't as bad as people make them out to be. They are still one of the cheapest out there. And remember, it is a KIT. Not a finished rifle. If you are handy, patient and knowledgable you can save some money by going with them since you'll be able to handle the problems associated with a cheap kit like M1S.
It is the newbies that should stay clear of these types of kits. It all comes down to expectations. People want CHEAP, KIT, and PERFECT RELIABILITY/FUNCTION. Hard to get all 3 of those, if not impossible.
At under $500, as the old saying goes - you get what you pay for!