I picked up an elven shield, equipped it and the shield is invisible. I dropped it and it became visible. Picked it up again and yup invisible. I'm sure the shield is there ( bumped against the wall and it made that iron sound).

Is this a known glitch?

Sorry, I don't use a shield. I think I used one very briefly during Dragonborn, but my Mage/archer has her hands full with a bow mostly, or sometimes a spell in one hand and a soul-trapping scimitar in the other. My follower Serana uses a shield I smithed for her, and it's always visible.

I gave my shield to Serana also. She equipped it right away and it's visible on her. Didn't bother testing more. I'm really pleased with the dlc though. I'm just in that "oh another glitch zone", not letting the little flaws get to me.