In the context of plaster and similar, "bom" usually means that it is not attached to the substrate, so I'm wildly guessing here and thinking it has to do with applying too thick a layer, which can create situations where the self-leveling compound won't be secure against the substrate.
Whether this can occur due to heat development, gases, or deformation during curing, I don't know, but it's perhaps possible...?
"Genom stansning" - here I suspect a slightly unfortunate separation and you actually mean "genomstansning," which would be that the surface of the light concrete element pierces through the compound. This can happen when there is a thin layer that doesn't hold together properly and the surface tension in the self-leveling compound, combined with irregularities in the substrate, interacts. It's a bit like poking a hole in a balloon and it shrinks.
