Mowlas, You were tremendously helpful. Thank you.
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The learning points are:
Preventative maintenance. Easy. Open window and spray the guides with silicon oil - its slippery and does not have an odour.
When it jams.
You will have to dismantle it to inspect it. Don't try touching the switch to move it. Expect to replace everything I listed above. Whilst the glass is out, clear the slots it moves through with your trim removal tool, then use lots of silicon oil spray.
Those are the really important points. Happy to explain in more detail. Just ask in this thread.