See https://commons.wikimedia.org/w/api.php?action=help&modules=managegroupsynchronizationcache which has
title: ⧼apihelp-managegroupsynchronizationcache-param-title⧽
group: ⧼apihelp-managegroupsynchronizationcache-param-group⧽
Looking at the results of a code search, it seems they've somehow ended up under "messageTitle" and "groupId" instead?