In the /mod/feedback/analysis.php, edit.php and complete.php there is a bug in certain type of questions that break the structure of the html:

• multichoicerated: In analysis.php when calculating the average it adds <tr><td>average: x</td></tr> without the enclosing table tag.

Then, if you have a custom theme that has a global <table> and the feedback is into this table it breaks the global table.