strange display of chords

Hi folks
I wrote some choruses together with chords.
After re-opening the file, the chords are displayed in a long, technical way:

e.g. Am6 --> A&display_minor;&six;

If I click on it, "Am6" appears in edit mode. After leaving the field, the display switches to "A&display_minor;&six;".

What could be wrong? Is it a setting?

Thanks in advance
Heiko