Reproduced in, when all config is imported, the shortcut third party settings for the seven theme appear missing schema and therefore the process fails and config is not imported.
fail: [Other] Line 162 of core/modules/config/src/Tests/ConfigImportAllTest.php: Schema key seven.settings:third_party_settings.shortcut failed with: missing schema
This issue was originally thought to be related to. The reason this surfaced at the same time is that failure left the test having installed shortcut and then uninstalled it. If the test works it would then go and install all the modules again thereby fixing the config again. However with this did not occur and then the final schema check once the test was over kicked in and showed us this failure.
User interface changes
Data model changes