Out of the box the govcms_zen theme prints the first sidebar over the top of the content area. It's very broken.
This was originally raised in #149 and that issue was closed however the issue was never actually fixed.
There was a pull request created at #254 but it seems that wasn't actually merged in.
That pull request also isn't really a fix, in that it doesn't fix the first sidebar, it just removes the first sidebar. So I'm not sure that is really a suitable workaround, but I guess it's better than having it there and broken. Maybe.
I'm not sure why the previous issue was just closed but this is definitely still a problem with 7.x-2.15. I'll check 7.x-2.16 but I suspect it will still be in there too.