Of note is also that one of the reasons Mandela gave for supporting Castro until the end was Cuba's extensive military support in Angola, that Mandela credited as a substantial source of hope for the ANC and a demoralising event for the South African military, and as a major contributing cause in the independence of Namibia.
After his release in '90, he visited Castro and heaped praise on him for that among other things. There's no indication that he regretted that support for Cuba's direct military involvement in open warfare later, as far as I know.
Here's an excerpt (with links to the full speech) of Mandela's speech on the subject at a commemoration of the start of the Cuban revolution in 1991:
https://www.democracynow.org/2013/12/11/nelson_mandela_on_ho...
(I have plenty of issues with Castro, but it's worth understanding why he was seen as we seen by African leaders, and how we was seen by people like Mandela also elucidates those leaders own views)