Tourist Visa Query

I'm currently in Cape Town on a tourist visa (UK citizen).

My partner and I arrived here on 3rd January planning to stay until 31st May. We had done some research and were under the impression that if we left South Africa before our initial 90 day visa was up for a period of 4 days or more, then we would receive a new 90 day visa upon our return to South Africa. I accept that we were slightly wrong here and you can no longer do this by visiting a country that borders South Africa.

We therefore planned a trip to Namibia for a week in order to renew our visas. Upon returning we were told that this no longer entitles us to a new 90 day visa and we are in fact only able to stay until our original 90 days expires on 3rd April. We were told at customs that in order to receive a new 90 day visa we must in fact leave the whole African continent before returning.

I have done a lot of research since hearing this and cannot find any official documentation that backs up this requirement. Various fora have seen some people having this problem beginning late last year, but still with others saying they have travelled to e.g. Malawi as recently as January 2017 and receiving another 90 day visa.

I have two questions which I would greatly appreciate advice on.

1. In order to get a second 90 day visa must we leave the African continent first?

2. If i leave SA for a neighbouring or other African country on 2 April (day before my visa expires) and then return on 4/5/6th April, will I receive a new 90 day visa?

Many thanks for any advice available!