A light fully glowing would be 120 volts. A light
extinguished would be near zero volts. A light glowing
partially would be something like 60 volts. But 'something
like 60 volts' must not exist between any two wires. So what
is leaking half of the 120 volts? That is basically the
question to be asked. Nothing should be leaking half of the
120 volts.

BTW, that tester cannot report a good wiring job. It can
only report a failure; not a good condition. But in your
case, something is leaking 'something like 60 volts' where
there should only be near zero volts or 120 volts. Maybe an
appliance. Maybe a wiring problem. But definitely a problem.
Maybe the symptoms of a minor problem or maybe symptoms of
something serious. Further information is necessary which is
why I would be using my multimeter to learn more. Start by
measuring voltage between every pair of those three receptacle
connections - 3 voltage measurements recorded for this and all
other electrically adjacent receptacles.

Zing wrote:
" What is the easiest way to test an outlet?

Use a receptacle analyzer. Leave the power on, but make sure nothing is
plugged into any outlet on the circuit, and turn off all switches on
the circuit. Now, plug the analyzer into the outlet. A series of lights
will tell you if the outlet is wired correctly and working."

I know of no one that does this or ever did this when using the tester.

If it is that important, I think it should be put into the instructions
with the tester.

Does that instruction make any sense ?
Might this be my problem vs something more serious ?

TIA again