I do agree with OP that a shop should respect your booking.

You are probably a gentleman, and sometimes there is a price to pay for being very nice and accommodating. Cant avoid the feeling that the shop took advantage of your good nature. That's fine, you guys have longstanding 'business' dealings

At a shop you like, sometimes you go with the flow. You usually have some future good times, to make up for the inconveniences

This issue I bet would be less likely if you punted at a quiet time. I know you can't do that

If you are booking at a busy time, the shop has a conflict of interest and unjustifiably will try to please multiple punters at once

That ML probably attracts a lot of clients. Good luck to her. It pays the bills. The ML you like is not just your favourite, but the favourite of another punter who books on the hour

There was a TV game show where the contestant is put in a tall narrow glass tank with money ($50 notes) flying around, and a fan on the floor of the tank blowing the money around the tank. The contestant had 1 minute to grab as much cash as possible

That my friend is the analogy for a popular ML at peak times in a shop

Not justifying it for one moment. You do deserve not to have your punt stopped 15 minutes early

Hope your next punt is a great punt