I have a Black&Decker electric hedge trimmer - you know the kind, with the
thumb safety, the index finger trigger, and the 2-3 ft long shears, which
operates on electrical power from a cord plugged into an outlet.

All of a sudden the unit keeps cutting off even with the trigger held. The
cord is firmly seated for electrical continuity. At one point I had severed
the power cord, repaired it, so was thinking it was the cord, but even with
a new replacement cord the symptom persists, and I do get the intermittent
brief "on" with the original cord. The original cord does provide power for
other things, so it is not the cord, but perhaps the severing shorted
something in the trimmer?

Here's the peculiarity: If I rotate the unit so that it is upside down, it
runs. As soon as I rotate it rightside up, it conks out again.

Any ideas as to what this is, and if it is easily repairable, or do I just
need to buy a new one?