If you hit skeleton twice between blocking your shield, it will hit through your block even with the shield fully out.

Step 1: Shield in survival with a skeleton nearby

Step 2: Hit the skeleton twice directly after deflecting an arrow

Step 3: Pull out shield before skeleton shoots again

What happens: If the glitch is happening, you will be hit by the arrow despite having your shield out.

What should happen: You SHOULD be able to deflect this arrow as well.

Notes: This makes it very difficult to fight skeletons up close. You will either be hit, or lose huge amounts of shield durability.