When I look at my /include/staff/ticket-open.inc.php and go to line 311 I see a closing table tag </td>
.
Same thing on github.
When I look at /scp/tickets.php line 526 I see
require_once(STAFFINC_DIR.$inc);
This is where the ticket-open.inc.php is included in the page.
Have you modified your version of osTicket?
I would re-upload the files from the download archive and make sure that they overwrite the source files in your folder:
/var/www/html/osticket/upload