Unable to reload postfix/Dovecot config

Operating system:
CentOS Linux release 7.9.2009 (Core)
3.10.0-1160.45.1.el7.x86_64
OS version:

Since some time I registered, some emails do not arrive anymore. I tried then to reload postfix, restart postfix and the problem is I get the error messages: "Error: 302 - Moved temporarily: reload.cgi, also start.cgi, apply.cgi.
Also the webgui starts to go in an endless reload loop with safari, “Errors occured on this site” trying to reload until it gives up. Is there any known bug in webmin?