I hate troubleshooting "blind" but Lambda unfortunately don't release much if anything in terms of schematics or other service information for their power supplies. The unit in question is a Lambda LUS-11-12 switching power supply.
I'm trying to determine what this particular component is (see attached picture). On the silkscreen it is identified as "SR1".
Out of circuit multimeter readings (diode test mode +/-, diode test -/+, and resistance respectively):
Pin 1 to 2: O/L, O/L, O/L
Pin 2 to 3: O/L, O/L, O/L
Pin 1 to 3: 0.04V, 0.04V, 79.5 ohms
My guess, considering what part of the circuit it's in and the "SR1" on the silkscreen, I'd guess it's some type of SCR. If so, then it would be faulty considering those measurements.
If anyone can positively identify this part it would be a great help!