Failing lens hood.
 

Seems Sony still haven't got this simple piece of camera design right.
The Z1 has the same problem. After a time the protective shutters jam, maybe only one will open and/or they close incorrectly.
This was simple enough to fix with the Z1. Open the unit up, put a small amount of graphite on the plastic pins where they are operated by the cams, operate a few times to grind the graphite into the pastic, clean off excess graphite and re-assemble. All our Z1's lens hoods have kept working since I've carried out this simple porcedure.
Today I tried this on a EX1 lens hood that's jammed. Problem I stuck was the unit in now sealed by the rubber section being glued on. I undid several screws but couldn't get inside. I could open enough of a gap to squirt a goodly amount of graphite in. I then blasted it around inside with some canned air. All got a bit messy but now the shutters open and close like new.
I can't really recommend this repair procedure as yet. I'm still finding the odd particle of graphite finding its way out of the hood and onto the filter everytime I open and close the shutters. It might take a lot of tapping, blowing, brushing and cleaning to finally get rid of all the excess graphite. Thankfully graphite is quite harmless.
If anyone else has struck this problem and found a better repair procedure I'd like to hear of it. The hoods are cheap however it seems they're all destined to fail so a way to make them reliable in the long term is what we need.