Once you equip it, You can’t take it off no matter what, Attempting to do so would unequip the weapon you equipped instead.
It happened to me too. Click on the wooden buckler, click unequip. Your weapon is unequipped instead.
I’ll look into this tomorrow. A temporary workaround to this is to equip something that’s 2 handed as it will unequip both your primary and secondary weapon. Examples of this are staves and bows.
This should be fixed now.