First a photo always helps, in offering advice. Sometimes an obvious problem can be spotted.
So while many feel, a hollow ground blade is easier to hone, pressure can easily become an issue with the flex of a hollow ground blade.
The problem of using pressure to force an edge on to a stone, is you have to apply the same amount of pressure in the same spot, through all the grits, something that is difficult to do.
So, first before you do anything, look at the edge with magnification, (which should always be your first step) and see where the bevels are not meeting, check for pitting. Ducks are notorious for Cell rot and the edge is the first to be eaten or weakened.
As said, the bevel is not set, or no-longer set. If you have a flat bevel, re-set it on the 4k with a rolling x stroke, check it with magnification.
If the bevel is not fully set, it will crumble on you in the later grits or even after the first stropping. You are not alone it is a common new honer problem. The importance of a fully and properly set bevel, cannot be over looked.
Here is a simple, non-destructive and 100 percent accurate, visual test for a set bevel.