When you adress a reminder to the pseudouser "assignee" it is shown in german as "Bearbeiter", which is correct.
But when you adress to pseudouser "watchers" it is shown as "Beobachter verwalten", which means "Manage Watchers".
Similarly, when you adress to pseudouser "voters" it is shown as "Wähler anzeigen", which means "Show Voters".
I think you grab the wrong i18n-Key, so you get the wrong display-value.
On the other hand, it might be not your fault at all, but a jira-i18n-Bug. That used to be quite common, historically.
Thanks for notifying us. Fix will be available with next release. We had got them from Jira 7.3 may be we should update from latest Jira.
The fix in Version 1.14.1 works perfectly. Thank you!