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In my case it was not the downgrade that solved the decimal point issue. This was my reply in that thread:
That was the issue. It seems the KDE update reset my locale settings to ZA \_en_ZA differs from the other languages such as af_ZA and no idea why), whereas I had mine for the ISO standard for ZA. But some tampering with it has got the currency and date correct now. And interestingly, the issue then with the cents rounding has also corrected itself (although I had tested that previously with both the comma and period, and neither had worked).
So it seemed to be locale based settings in KDE. I had to play around with the optional locale variations for my region.