Upgrading to Ligtroom classic 12.1, RGB color readouts were completly off on masks. Visually you could see the expected changes in contrast, brightness, etc while mouse over readouts showed the same numbers as before. So completly off. Like you could see that black areas were getting toward complete black, but the readout was still at around 14% in all 3 channels.
I downgraded my Lightroom to previous 12.0.1. which works just fine.