When on a Ticket History page, selecting Check-ins from the menu returns:<br>
<b>"No such ticket: <short_uuid>?=ci"</b> with short uuid of the selected ticket.

This results from the incorrectly formed url for Check-ins menu as:
"/tkttimeline?name=<short_uuid>?y=ci"

To demonstrate the issue, try selecting Check-ins link in history of ticket