Losing Highlight detail when adjusting curves

I have come across an odd one using curves to recover highlights on a clip. An over exposed white dress clip, but detail is there on parade when clip is dragged in. Once i start to adjust the curves to pull highlights down, it seems to glitch and the highlight peaks then flatline, as if blown and then can't be recovered just turning grey when pulling highlights down. It seems intermittent and can also happen when adjusting the col temperature or saturation using the wheels too. When it happens, if I do control Z, the problem is undone and highlights no longer blown and detail returns! I have repeated this many times in testing. At first i thought i'd really blown the exposure, till i checked the clip in premiere and realised the detail was infact there, which was a relief!

Have never experienced this behaviour in previous versions using resolve since 12.5. Anyone else experiencing this? Still loving 15 though!

Am on v15 studio Beta 2, windows 10 pro, etc as per signature.