Yea, sometimes my little shaper refuses to continue when using a wide tool. When that happens I swap to a sharp pointed 'V' tool tip and once it has a few 'scratches' in the work I change back to the wide tool and carry on.
I suppose once the tool skips, jumps, or whatever a couple of times it has put transverse ridges on the cut which cause the tool to skip and jump some more, I think of it like the effect of corrugations on a dirt road.
BTW, with my little shaper I had no success whatsoever with cutting slots, I only had to over feed by a tiny amount and it would all go to custard and reducing feed would not recover the situation. So I fashioned a fitted an automatic down feed and alls well.