No i18n translations within teasers

Hi!

We are using the AEM teaser system (experiences, campaigns, segments under cq/personalization). A teaser's content at the end is a parsys filled with custom data. Within this data we are using i18n resource strings with <fmt:message key="some_key" />.

Under my local environment (localhost:4502) the keys are replaced by the translations, like expected.
But on our deployment-targets (e.g. AEM Publisher) the i18n-resources are not translated. Only the resource-keys are displayed, like when the key would be not defined. But is is! All other texts on the page are translated properly. Only within teasers the translation does not work?!

Has anybody an idea? I appreciate every hint!

Cheers,

Hendrike