Upgrade from 7.11.x to 7.12 the icons are messed up

In some SuiteCRM installations after the upgrade from 7.11.x to 7.12 the icons are messed up.
The html code is correct but they are misinterpreted.
I had opened the post in collaboration and development
https://community.suitecrm.com/t/wrong-icons-after-upgrade-7-12-1/82997
maybe I should have opened it here?