Cape Town's prevailing summer wind, known affectionatelly as "The Cape Doctor", plays havoc with cruise ship schedules. The problem is that when the wind speed becomes too strong, Cape Town harbour is closed. This means that cruise ships are either stuck in the harbour and can't get out, or shut out of the harbour and can't get in (an unexpected longer cruise bonus for those on board, but shorter for those waiting for the ship!). This happens very roughly 10% of the time (based on feel rather than numbers, which aren't readily available).
In response, MSC Cruises, who are by far the largest operator of local cruises in South Africa, have steadily decreased the number of cruises which they operate from Cape Town. Most of their cruises are operated from Durban, where it's rare for the the harbour to be closed as a result of wind, the water is warmer (pools on the ship are filled from the sea) and there are pretty island destinations.
The most recent victim has been the MSC Musica which, on the 24th January 2019, could not enter Cape Town's harbour due to gale force winds which were gusting from 40 to 50km/h. The Musica was travelling from Walvis Bay to Cape Town, and it's ongoing trip would be to Durban via PE. It eventually got into the harbour two days late, on the 26th January 2019; with passengers having to hole up in hotels for a couple of days.
Be sure to take out travel insurance, as it's not always clear what your compensation will be for things going wrong.