Welcome. My name is ***** ***** would be glad to assist.
It definitely sounds as though you have a loose connection on the circuit.
Any loose connection can create a dimming or failure on the circuit, whether it is in a receptacle
or switch or breaker. All cables in the home, are installed from one item
to the next. So even if the switch is good and screws are tight, the wire
that powers that switch comes from a receptacle possibly with a loose
In order to determine where this may be located, a 2 lead multi meter certainly helps instead of opening boxes one
at a time to find the failure point.
But either way will work.
Make a map of the items on the circuit breaker, by first logging what is off when the breaker is off and then again, with the breaker on, what is off.
This helps to see if something on the breaker is still operating. An item working can still be the problem area, as it may have power in, it is not applying power out.
One test for loose connections in outlets, is to get a lamp with a low wattage bulb
and plug in the outlet.
Take another lamp and move around the room or adjacent room and plug it in---
You then jiggle/shake the plug back and forth left to right and see if either lamp flickers
If it does, you have a loose connection.
The problem can be in the receptacle before the problem one or in the same one.
If you get this at a Home Depot or Lowes for $4, it is a life saver
for checking outlets. Same thing inspectors use. Easy to jiggle the outlet too.
Remember, just because an outlet works does not mean that it does not have loose wires.
Outlets have power in and power out.
Same for light switch boxes and light ceiling boxes. But the lights and
switches have to be removed to find loose connections.
Try that test first and see if it pinpoints the problem location and then we can work from there.
Thanks, ***** ***** me posted