When you lay down cause you're wounded and you want to heal up while having binos/pistols in your inventory as soon as the healing animation is done it switches to the secondary/binos instead of the primary and you can't move/stand up during this process.
Same goes for looting with binoculars. If you're done looting and close the inventory it switches to the primary then to the binos again and you can't move until the animation is done.
(Battle Royale player)