Why Bakerloo line trains occasionally call at Kilburn High Road station

It’s very rare, but on odd occasions, a Bakerloo line train can be seen at Kilburn High Road, a station it doesn’t usually call at.
To explain the situation, it helps to understand the layout of the Bakerloo line in the Queen’s Park area.
Track layout diagram (c) TfL
The tracks heading north emerge from the tube tunnels between Kilburn Park and Queen’s Park stations. Just past Queen’s Park station, there’s a large depot shed that the trains pass through to hea