OnlyOffice cannot load some documents

Dear all,

I have NC 18 installed and the community document server. Some documents can opened as usual, but there are some documents, that cannot be loaded. Only Office is opened, the message appears that document is loaded - also 100%, but then nothing happens. In German the message is: “Dokument wird geladen… 100%”. And thats it. I cannot find some errors in log.
Do you have any ideas what I can try ?
One thing I have changed last week: we have an official certificate from godaddy. As I needed a certificate for another subdomain, this certificate for that server has been changed. I changed it local. Is it possible, that I have to add something for document server as well ?

Unfortunately I cannot add extract from my log here. If somebody give me a hint, how I add a txt-file here, I could show an extract from log as well.

Thanks and best regards