[Warner306]

That sounds like a source with banding or a display that causes banding. Your projector might have difficulty with smooth gradients. That wouldn't be that uncommon. If you are watching HDR content, tone mapping (HDR -> SDR) will cause posterization by deviating from the PQ curve. Not every display will create banding with a 12-bit input. The new 10-bit panels don't all process high bit depths very well and many are actually 8-bits plus FRC and no one knows this. Your 1080p projector would likely be 8-bit, anyways.

Did you test this on a gradient test pattern or with some source content?

If it is source banding and it looks bad, set debanding in madVR to high. That is only way I know of to reliably get rid of source banding without leaving something behind.