While casting from strafe to hungering arrow, the momentum buff will disappear. You can then keep firing Hungering Arrow and momentum will pop up for a second and cancel out again. The only way to get momentum to work again is to either die our enter a new area. It is not to hard to work around, unless your in a Greater Rift. Your defense drops during this causing almost instant death, which I imagine would not be good if this is happening for Hard Core players.
Me to. Am a casual player, just earned my GoD set and the Momentum icon will appear briefly, no stacks generate and it disappears after a few seconds, it then does not appear again at all unless I go to a new area. Playing on XBox Series X