I have run into this with my little jet some years ago. The solution was a very small piece of dust in the taper that holds the chuck on the taper adapter. I cleaned that and cleaned the mt tapers on tail and head. most of the problem went away. The second problem was me. I advanced the bit too rapidly bad news for brad point bits. l slowed my feed rate down and switched to normal drills and started in a divot made with a skew.