As per subject - and discussed in #1782, it has been reported that Hub launched servers that have an admin user (i.e. in the web app) and the password set in the Hub starts with # will fail to allow log in.
This has been reported specifically against the Odoo appliance, but almost certainly applies to others.
Also it has been noted that this DOES NOT occur when setting password via inithooks, so appears to specifically be a Hub bug.