GeNOS,
I've never experienced what you're seeing in the situation you illustrate. And, Barry, I've never had the intersection priority of the layers of the cutters vs the targe make a difference.
I've subtracted a dozen slabs from a mesh many times without problem. The only time that things didn't work was on a project back in 9 or 10 where one slab had a spline-like edge (multiple adjacent curves), and it just wouldn't cut until I split the slab in two.
You mention that a different slab is the problem depending on how you select them. Have you tried selecting half of the slabs, for example, doing the subtract, and then selecting the other half and subtracting them from the mesh? Do you have a problem with each half, or just one half (of the slab total)? If just one half, undo all operators on the mesh, and repeat subtracting all of the slabs that worked as one operator, then half of those that didn't work, and then the remainder (three subtract total) ... until you can track down something reproducible...
Good luck,
Karl
AC 28 USA and earlier • macOS Sequoia 15.3, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB
One of the forum moderators