Hi Kyran- in your larger model the cutting curves are deep enough that they cut into the core of the handle. You need to be careful about how you draw these so when they push through and cut the material of the handle, they leave some thickness. Yours are red here, I suggest using something more like the green - that leaves at least a little thickness at the base of the cut, but I’d make the inner core a little smaller to keep the thickness a little greater at the minimum.
There are other/better ways to get at this, I would say, but given where you are now in the project, I’d do it as I indicate, I think.
Does that help at all?
-Pascal