[Koha] Cover upload fails

[uwe]

Hello, 

I would like to figure out a problem with my koha installation 3.18.01
on a debian wheezy server (installed with apt). Cover upload fails with
ending up at "Upload progress:100%." (this means that the page is
missing the forms to choose the biblio number and the save button).

I found nothing in my server logs but Firefox JavaScript console says: 

> "Load denied by X-Frame-Options: 
> https://xxxx.xxx:8080/cgi-bin/koha/tools/upload-file.pl does not 
> permit framing. TypeError: jQuery.handleError is not a function"  
> (ajaxfileupload.js line 86) 

Thanks for some hints to solve the problem.

Best wishes
Uwe