Dead track area dcc = Get Physical
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I agree, you may have a bad connection that is not visible. A weak, oxidized contact can give a good meter reading since meters require very little current to operate. Motors require a lot more and a weak joint will not pass it.
Mechanically clean the rails by scraping or sanding. There maybe a coating or corrosion that the usual rail cleaners may not touch.
Try redoing the wire to rail connection if there is one. Unsolder it, clean the area including removing old solder, use additional flux if you can.
Try moving the rail joiners. use a little contact cleaner applied with a toothpick or such.
Solder/re-solder the rail joiners. If you need to, replace the joiners and solder.