In addition to the items Gcap lists, this can also happen if the paint is a water-borne paint (almost all are these days), and it is thinned out too much. If that's the case, the paint will need to be stripped down, and fully reprimered and repainted. Fingers crossed that it's not this issue.

Living room: 818v3, Audio Research D150, Maggie 1.6
A/V room: 861v8, DSP7200SE L/R/C, 4x DSP320 surrounds, ID41 + Roon, UHD722, Prime+PS