Cockpit 0.62 contains a number of compatibility fixes.
In particular, bugs were fixed that caused adding and using servers from
the dashboard to break. One fix was on the bridge side and the other on
web service side (ie: both hosts need an update).
Prior to 0.62, different versions of Cockpit may not work well with
another between servers. There are many prior versions where this
limitation does not apply, but it's a good general rule.
In addition there's a fix in 0.62 which fixed compatibility with docker
1.7 and later:
Another fix will be along shortly to fix generation of certificates for
old versions of NSS:
Hope this helps with packaging and diagnosing issues.