If I right-click the "Cut" item and then "Mark to recompute" nothing changes. There error icon is still there. Same behaviour when I select the document root and right-click "mark to recompute". How did you "recompute the whole document" ? Is this a menu item somewhere?
If I hide all the other items except the cut, I have an empty screen (because the "cut" operation failed).
I just found out, that if instead of the Part->Boolen->Cut operation, I use the Part->Boolean->Boolean... operation it fill fail for all methods with the error message "Performing intersection on non-solids is not possible".
So it seems the 3D-Offset generated a non-solid object. But why? It looks like a pretty decent solid to me.