I haven’t run into this problem with OF, but once or twice I’ve had other applications that failed to update. My solution has been to download the current version from the developer’s website and then install it over the older version. If you haven’t tried that, it might help.
It is positive as these errors often mean that the app was successfully able to contact their server and download the compressed update file. The way is installing the latest version of the app manually from Omnigroup,s download page.