Well, you ask for one thing. Some of the obvious things that spring to mind for many, I'm sure most have mentioned.
That said,for me, the only thing that springs to mind is the customer agents always throwing me a the standard buck as compensation for something that wasn't added properly. I had it a few times with xmas calender promos and some deposit free spins through the years that didn't add upon deposit.
It's a little disheartening spending time to explain some spins or a promo spins type wheel werent added, and then having them say they'll compensate the value in bonus funds, to shortly be thrown £1 (in my case, I think it was possibly newrly everytime they were valued over £1 iirc, and so often i just accepted the £1 and forgot about it). Though obviously often when it happened to me the spins value was not over £1 anyway, unless they were 20p value or over ten spins. So the standard £1 compensation works quickly and like a charm in many cases.
But then, for free spins with higher total values, or a free spin wheel promo that didnt work when opening the slot, where the value of spins were, for example; when given the free spins wheel on gonzos quest for bankruptcy, spins holding a value of anything between 60p-£4 depending on the outcome of amount give on the wheel. and the standard £1 compensation drops into your balance after the line "i will add the value of the spins as bonus funds instead" was the response from the chat reps.
Nothing against your customer service, always been on the ball as far as im concerned. But doing that after saying they will credit the value of the spins as bonus funds does kinda make you feel a little like the person dealing with your query isn't too bothered about you (which im sure isn't really the case having dealt with them many times), and although the extra 50p, £1 or even a possible £3 that you might occasionally be missing out on in that situation unless you go back and persist for the full value, isn't likely to change your life, you still feel like a pleb if you consider going back and asking again.
It's no biggie, its not really the money but rather the way you're left feeling like a begger when it happens. And tbqhwy, I can't think of anything else that hasn't already been mentioned.
ps. If you even consider for 1 half of a millisecond on adding exactly £1 bonus funds to my account for this epic, revenue improving post,
I will find you.