Stop adding Auto-LUT
Your auto-LUT feature should be disabled or enabled when opening the program. If you cannot do this it is absolutely maddening.
I don't think this is from applying a LUT. Is the footage from an iPhone? I'm wondering if what you're seeing is explained by how we've started supporting HDR footage. See this video: https://youtu.be/odwptnEhxJs
R S commented
This raises the issue of how you've implemented HDR support.
If a clip is set to HDR and the timeline is set to rec 709, it seems intuitive to me that colour management would represent HDR in a 709 space (ie. "compress" the HDR to SDR).
The intuitive sensibility: If I have a colour clip and I place it in a black and white timeline, I would expect the clip to look black and white. So too with HDR/SDR.
The current implementation is both unintuitive and unhelpful.
The timeline colourspace should be displayed. Arguable clip colourspace should also be displayed. Mismatch errors should also be displayed. These could be (toggle-able) overlays or simple displays (like the current way timecode is displayed).