A formatting issue may be seen in the Portal on an Interactive Documentation page which was generated by a WADL. No errors are seen in the logs as it is just a formatting/display issue.
In the /SYSTEM/conf/properties.xml file, the property named enableHtml5InEditors may have a value of "no" instead of "yes". A value of "yes" is default, so if the value shows "no" then it was customized.
This impacts all API Portal versions 3.5 (including CRs) and older.
To resolve, the value of the enableHtml5InEditors attribute in the /SYSTEM/conf/properties.xml file will need to be set to a value of "yes" so that it should read as follows:
<Property name="enableHtml5InEditors" value="yes" />