Sony 24-70 GM MK1 stopped autofocusing - makes woodpecker-like sound

Whenever I connect the lens to the A7IV, it makes a constant 'woodpecker' like sound.

The aperture number is showing F-- and it doesn't autofocus anymore, nor can I use the manual focus ring.

I did try a DIY repair opening up the entire lens and getting right down to the focus group assy and after putting it back together it started to work for the first time I connected the lens back to the body - focus, aperture, zoom all worked fine.

When I disconnected the lens and reattached it, it went back to the broken state - not sure if the first time I reassembled it back, something inside reset to it's initial position before failing again.

Is this an outer barrel issue, damaged flex cables or do I need to replace the focus group assy entirely?

UPDATE: I've got the lens somewhat working! See the comment here: [https://www.reddit.com/r/SonyAlpha/comments/1uedcy7/comment/otmustt/](https://www.reddit.com/r/SonyAlpha/comments/1uedcy7/comment/otmustt/)