German syllable

hi,

I am using wp simple booking calender in german language. Some of our users fill in their names in the booking form, which I then copy/paste into the booking details when accepting the booking request. Quite often, names contain syllables like ü,?,? (ue,oe,ae). They first appear correct in the tooltip, but after a while (hours / days), instead of ü,?,?, strange combinations of letters appear.

The same is true, if I use form labels containing these syllables. So it seems, that the system does not accept these special german characters.

What can I do? Can I change a character set? Any hints?

Kind regards

Franz