rejoice my friends, for I have solved the mistery of the red boxes
Ok, in SU23 there is this new panel on the side, in french it’s incrustation, I think it’s overlay in english ? it allows you to have a selection of plugins always on.
you have the Solid inspector overlay on. The red boxes are here to yell at you “THIS IS NOT A SOLID”
I had pretty much the same case right after updating :D. to stop it, untick solid inspector in the overlay panel 
