Does anyone have some ideas?
As I recall, this is a Kerberos problem. Do you have NTLM enabled?
https://www.bing.com/search?q=windows%20share%20kerberos%20logon%20failure%20ip
By default Windows will not attempt Kerberos authentication for a host if the hostname is an IP address. It will fall back to other enabled authentication protocols like NTLM. However, applications are sometimes hardcoded to use IP addresses which means the application will fall back to NTLM and not use Kerberos.
The simplest solution is to just use the server name and not the IP address.