No Output with German umlauts

Hello again.
I would like to ask to double check the following issue:
If I have German umlauts like ?, ? or ü in the output string the entire string will not be added.
For example, please add as city from the vendor “Zürich” and print the label. In my case the city is missing. If I change it to “Zuerich”, everything is as it should. Same for the shiping to address. If the city is “K?ln”, the city string is missing.
It happend if “Check this to enable Cyrillic encoding” is checked as well it is unchecked.
Could you please double check and give me a solution for this?
Thank you.