Gerrit and Jenkins seems to be behaving oddly recently, claiming that patch cannot be merged, or that it needs rebasing when it is actually up to date. Please see https://gerrit.wikimedia.org/r/c/mediawiki/extensions/UniversalLanguageSelector/+/690494
Merge Failed. This change or one of its cross-repo dependencies was unable to be automatically merged with the current state of its repository. Please rebase the change and upload a new patchset.
Similar but perhaps unrelated issue happened on https://gerrit.wikimedia.org/r/c/mediawiki/extensions/WikibaseStatementUpdater/+/693578/1 where Gerrit's rebase dialog claimed that the change was already up to date with the master branch, when it was not. It did allow rebase though, creating PS2. For those ULS patches it does not.
Not sure if it is related, but I recently deleted and created a few branches for the ULS repository using the Gerrit interface. Could this have broken something?