Check under the machine (or remove any panel) to se if anything obvious has dislodged like a spring.  

I'm wondering if the escapement mechanism is dirty and has stuck in a position which effectively means the carriage is continually free as opposed to being locked into each respective tooth of the gear.

I don't have a Stirling, I have a Super, but mine is exposed underneath.  If yours is like mine, the escapement is the geared circular toothed wheel at the bottom middle of the underside of the typewriter.  Have you attempted to clean the machine yet? maybe dust off the machine very carefully with a brush, making sure you don't knock off any springs.  I don't like compressed air because it can blow dirt further in.  Then when the machine is clear of removable debris and is just oily and sticky, clean it with white spirits, making sure you don't get any on any of the plastic keys or finish.  Do this outdoors as it gives you a headache.  Use a clean brush and apply to all the metal moving parts, wiping any other parts with a lint free cloth. Keep moving the various keys on the keyboard so that all of the parts get a good wiggle whilst they are damp from the white spirits.  When the machine is spotless, wipe it dry.  I use a hair dryer and have never had a problem, but, white spirit is highly flammable so you do this AT YOUR OWN RISK.  Once all the white spirits has been evaporated away, very lightly oil any moving parts with the tiniest of drops of high quality oil, like sewing machine oil, or gun oil. If you're not sure whether to oil it, check in with us.  Over oiling or oil in the wrong place can cause further problems.  Don't use grease or cheap oil.  This hopefully should free up the mechanism.

 

Platenboy wrote:

If you want to show any pictures of have any specific questions, you can message me privately and I'll be happy to help.  Replies can be slow or non-existent on here (if nobody knows how to help)

FYI, the Super Sterling is an electric typewriter. And the point of having an open forum for repair issues is that it might help others later on who encounter a similar problem. If you resolve this particular problem through Private Messaging it won't be of any help to others.

Yes.