Strange artefact with Mobile HDR

UE4.22 Github version on Mac OS

My game is a mobile game, with one directional movable light and one directional static light and a sphere reflection. No Skylight, no post processing. I just wanted some light and a bit of shadows

Whenever Mobile HDR is selected, I have a strange artefact on the viewport. Some kind of screen centered, concentric circles. I thought it was only on Viewport but the same happens on packaged game.

This disappears if I take Mobile HDR off.

I have tried various light settings but can’t make this go away. Any hints?