I play on PC with a controller. I don't know if it's a general thing or specifically with the Drifter, but when using their weapon I noticed I can't reload properly while moving, and the Ammo UI for the weapon disappears when the 'show ability menu' button is pressed. When I stand still, reloading and activating overcharge works normally. If I have "Drifter mode" preselected on my abilities and tap to use without bringing up the ability menu, the weapon's ammo will show, but will disappear again if I bring up the ability menu.