That is very unexpected. What changes? Worst case is to “show config outfile” and then verify the config and boot the config by “configure” command.
You can also try show config outfile and find those changes there.
From my experience the issue will be different. I guess the config was not changed by WEB but some dynamic protocol changed the behavior. Example: new VLANs were learned through GVRP...
The web on S-series is very limited = it should be quite easy to verify those sections with show config and show feature by feature. By show vlan you will see what vlans are used by show config vlan you will see what was configured.
Regards
Zdeněk Pala