I had that too last week, took about 20 minutes to finally clear so I could rebook at the cheaper price. I was on edge thinking I'd lost out on the excursion whilst trying to save some money. Didn't do that a couple of months ago
Last week went on 4 night cruise on Ventura, had flexible dining - dining app was not in use. We tend to eat early and had no issues with dining on a table for two and no waiting
It was fine as we were a family group on a table for 6, also it was a round table so there was distance between the tables, waiters were the same throughout