If you have a shulker with both silk touch and fortune pickaxes or normal picks it always grabs the silk touch ones, even if there's already a fortune one in the hotbar as well as a silk touch it will refuse to use the fortune one. And occasionally if there's a silk touch in your inventory and a fortune in your hotbar it'll either grab shulkers from your echest that contain other silk touch picks and grab a second one or it'll grab stacked shulkers that have both or at least silk touch pickaxe sand fill the inventory with silk touch
If you have a shulker with both silk touch and fortune pickaxes or normal picks it always grabs the silk touch ones, even if there's already a fortune one in the hotbar as well as a silk touch it will refuse to use the fortune one. And occasionally if there's a silk touch in your inventory and a fortune in your hotbar it'll either grab shulkers from your echest that contain other silk touch picks and grab a second one or it'll grab stacked shulkers that have both or at least silk touch pickaxe sand fill the inventory with silk touch