PRP

For people who need crimping assistance the battery centre in Fourways Crossing did mine for free. 

Are these older models? Or are some nearly new?
I'm not familiar with the NCE brand. It could be that they are junk, I would not know. The datasheet says that they are 85 V 160 A parts.
The IGBTs pictured are ST brand, and are well-known good quality. If and when the MOSFETs short, that seems to send a surge through the transformer that tends to cause the IGBTs to fail.
The MOSFETs are protected against inductive spikes by the electrolytic capacitors nearby. That's why it is suggested that these capacitors be replaced with quality parts with a long rated life. Both my inverters have 100 V rated MOSFETs and 10 000 hour rated capacitors. It's possible that recent capacitors that they are using are junk. The shortages are probably not limited to semiconductors.
It's also possible that the frequent load shedding is causing transients on the AC-in port that could be destroying the IGBTs.

For people who need crimping assistance the battery centre in Fourways Crossing did mine for free. 

Thanks I have but he is flat out at the moment. 

For people who need crimping assistance the battery centre in Fourways Crossing did mine for free. 

Look here 
https://www.liteglo.co.za/product-category/circuit-breakers/?filter_circuit-breaker-application=change-over-switches&query_type_circuit-breaker-application=or&product_orderby=price
 for some ideas

Interesting article on the heating cost 
https://www.capetalk.co.za/articles/409118/opinion-the-cost-of-making-a-cuppa-tea-gas-vs-electricity