Upgrade from 9.1.0 to 9.1.2 causes cURL error 51: SSL:

verbose, the error message shown on a blank browser window is:
cURL error 51: SSL: certificate subject name 'my.domain.name' does not match target host name 'internal.ipaddress.of.server'
This happens when I call my server via its private IP address.
When I call my server via its public url, I get the following error:
cURL error 51: SSL: no alternative certificate subject name matches target host name 'localhost'

I applied the necessary upgrade patches, checked my SSL setup with www.ssllabs.com routines (and came up with an A+)
I am at a loss - and have to admit that I am not very knowledgeable in terms of SSL.
Any ideas?

Hi,

just don't waste your time with the updater app and do the manual upgrade directly to the latest 9.1.4:

https://doc.owncloud.org/server/latest/admin_manual/maintenance/upgrade.html