Addendum.

I think a part of the problem with (South Asian) customers is that they make crazy-ass requests that you just can't anticipate, even coming up to your elbow to do so, or doubling back and changing what they had just said and had set in motion, so they catch you off-guard and push and push and make things go their way, and it's like the chaos puts you in situations you've never anticipated ,and since you always try to please the customer, oftentimes they can get away with really whack demands.

I think in the future when any customer comes up to interrupt and change their order as we key it in, I'll be deferential, but later go the table and reiterate that these things happens etc. etc and we try to honor requests, but we do ask that they try to have their full and final orders together when they give them at the table, since interrupting someone at the computer can lead to mistakes and delays, as can asking the kitchen to change something once the order has been sent.

I also think I had been assuming that people were overall listening to me, when they don't necessarily do so. 

With customers like that who come in late, I need to state what I always do, and if they're hemming and hawing at the table, reiterate that we need their order now, or the appetizers that they can give us, and reiterate the meal strictures, especially if they start looking elsewhere in the menu, and if they seem insistent, maybe say something like "it is the time of night where you can have a quick bite here, but it seems like you're looking for a wider variety of what we usually offer -- perhaps you'd like a few more minutes to decide, and order something for takeout, since we can make everything on the menu for takeout?",