Hi heavensrest – I’m sorry any suggestions have not been forthcoming. I would hazard a guess that the expected data is getting dropped along the path followed to actually register the booking. Users go through a number of pages after selecting guests and dates. It’s not unheard of for such data to get dropped when one is forwarded through multiple pages.
As a debugging process, you might try using your browser’s network developer tool to inspect data passed through each step. I’ll wager it disappears somewhere along the way. If so, it doesn’t tell us what’s actually wrong, but it greatly narrows down where to look for the problem. I hope this helps some.