Negative volume after solid difference

After making a solid difference, I get brep with a negative volume, which is impossible. How can I get the right result? (Grasshopper 0.90076)

any idea with this strange brep?

Any hope of seeing the file that causes this? I did fix a negative volume bug a while ago, what version of Rhino are you running?

(Grasshopper 0.90076) Rhino 5
Is there a workaound?

Is the volume wrong other than being negative? You could use an absolute component to fix it. There have been various negative volume bugs fixed in Rhino in the last few years, so if you post the file I can see if this still happens in R6 and R7.

if you subtract the whole item it should be not smaller then 6100.5003-0.03. So the value is also wrong.

I need a magnifying glass to read the values from your screen shot… It looks like:

6100.500655 - 0.033128 = -0.151017

Which is absurd, of course. As always though, this would be much easier for David and everyone else if you internalized your two geometries and posted an abbreviated version of your GH file.