I tinkered with this a bit more. There's something in the href that causes the save to fail.
This saves the changes but does not redirect:
"<a id=\"saveButton\" style=\"background:#6bbd57; border-radius: 5px; padding:8px 16px; text-decoration:none; color:#ffffff; display:inline-block; font-size:14px; font-weight:bold; text-align:center; white-space:nowrap;\" onclick=\"DoSave()\" href=\"#\">Save and Return</a>"
This redirects but does not save any changes:
"<a id=\"saveButton\" style=\"background:#6bbd57; border-radius: 5px; padding:8px 16px; text-decoration:none; color:#ffffff; display:inline-block; font-size:14px; font-weight:bold; text-align:center; white-space:nowrap;\" onclick=\"DoSave()\" href=\""&URLRoot()&"db/"&[_DBID_SUPERVISORS]&"?a=dr&dfid=10&key="&[Supervisor]&"\">Save and Return</a>"