Although I haven't really done much CRH in probably close to 10 years now due to time limitations (mainly my other hobby taking all my time), I thought I would add my opinion as I think it may be relevant here.
When I used to buy bags off the coin machine, I tended to buy almost all bags the bank ever had (except quarters and small dollars) as I would stop by every week just before they were picked up to maximize the amount of bags purchased. As such, if the coin machine was off, the bank would have no way to know unless I told them as nothing was ever verified by another service. I didn't report every bag that was off as almost all of them were off slightly (sometimes up, sometimes down) due to miss-sorts, foreign coins, and junk that got counted as coins. As a result on average I would guess I was slightly short, but I figured that was just part of the cost of buying bags instead of rolls. However, I liked the bags as I felt they provided me with a wider selection of finds. That being said, I did tell the bank when bags were off by more than a certain amount when I would pick up the next week. My threshold was either $1 or $2 in a $50 cent bag in either direction, I forget which.
I always offered to pay them back any overages and always ate any shortages without complaint. They never accepted any payment for the overages as they only paid the customer cashing in the coins the amount in the bag. In other words if 20 dimes ($2) got cashed in 20 cents ($0.20), they only paid out $0.20. In other words the bank was not out money. That and there would not have been a way for them to account for why they were taking in the cash in their system. Typically, the main issue was with dimes getting sorted into the cent bags if I remember correctly and that was known to be something that was the first thing to need tuning by service techs. From my understanding of the system, typical coin machines require tuning every so often. Frequently when I reported a certain level of miscounting, the lead teller would tell me that they would have service in and usually by the next week it was back to more correct. While I didn't track it, it seemed to happen every few months, or perhaps it was after a certain amount of volume through the machine.
I guess my advice would be if you are buying all their bags all the time, I would definitely say something when off by some amount like a $1 or $2 or more in a cent bag as it will help build trust. If only buying the occasional bag here and there, it is still a good idea, but not as critical as they will probably catch the counting issue through their armored service.
