We have a sharepoint 2013 running utilizing document set homepages as core part of our site.
For example, we have CSWPs on this site which display related items and recommendations under the "normal" document set web parts.
Now we want to adapt the layout to make it more pretty, and we are editing the home page via Sharepoint Designer. The correspoding files are in the _cts folder and usually named docsethomepage.aspx
Since we are changing the template, we are editing in "Advanced Mode", but whenever we save the page, all Content Search Web Parts are broken with an error of
Web Part Error: Unknown server tag. Correlation ID: 93fda89c-d4c0-b0dd-3895-84e9d6acc991.
How can we prevent this from happening? What is the reason that these web parts get broken by Sharepoint Designer?