Can't close gates, can't collect Sigil Stones.

[Polyphemus]

I can see the Sigil Stones - my cursor higlights them, and offers the action key.
When I press the action key, the animation runs, the stone shrinks, then disappears.
Then... nothing. The gate does not close, the Sigil Stone does not appear in my inventory.

This happened with the Sigil Stone at Kvatch (I had to close the gate with a console command), and it has happened with every gate since. I can't close any of the gates, and I can't collect any Sigil Stones.

I see the Sigil Stone.
https://steamcommunity.com/sharedfiles/filedetails/?id=3480322680

My cursor highlights the stone. I activate it, and the animation starts...
https://steamcommunity.com/sharedfiles/filedetails/?id=3480322861

The stone disappears, and... nothing. The gate doesn't close, and I don't get the stone.
https://steamcommunity.com/sharedfiles/filedetails/?id=3480322984