As an ex dealer, I have seen such situations many times.
Customers bring back product with faults that we are unable to replicate in the shop, we would always try to play the unit there and then, in front of the customer if at all possible. In the case of an obvious, replicable fault, a new replacement would be supplied immediately or if out of stock, ordered in. Simple.
But in a surprisingly large percentage of cases the equipment would work perfectly, in such cases we would suggest that it is left running for a while and perhaps collected later or the next day. Most customers were comfortable with this, assuming, usually quite correctly, that they had not installed/connected the equipment correctly. They would take the item home, install it with a little extra care, and that would be the end of it.
Very, very occasionally it would be an actual intermittant fault, actually quite rare in decent equipment in my experience. Mostly it would be some form of installation issue, sometimes but really not that often, a 'rogue' faulty product.
This is what the dealer sees on a regular basis, 'finger trouble' is far and above the most common reason for new equipment issues, that is the reality for any dealer and it is the first thing that any compedent dealer will check out. Simply playing the item is the simplest, quickest way to do this, most genuine faults will be immediately apparent, you do not need a technician with test gear to do this.
That is the reality of the situation, the dealer does not know the customer and his experience tells him that it is most likely finger trouble, and it makes perfect sense to check this out first.