Ok, first let me explain the difference between the little SSP50 and the PT-50C or the HW-50C
The SSP has MOV's that clip spikes. that's all it just passes the power through but it can clip spikes., .it also tests for some wiring issues (park side) and reports them (The LEDs)
The HW and PT-50Cs also monitor voltage and some other stuff and if they observe a problem like a 30 amp rig pulgged into 220 volts, or a brown out they protect you by shutting you off.
There is ONE possible error in manufacture which I would be real surprised by that can cause a problem
Here is how to test it.. On a 50 amp outlet you should see 240 volts side to side and 120 side to top or bottom (either side)
Use volt meter.. Plug it in, Wait for it to time in (that's a time in, not out) and measure voltages after it clunks. If you get 240 size to side and 120 side to top or bottom (both sides) the problem is NOT with your PT-50C
If you get 240 either side to top or bottom Problem *IS* with the PT-50C
NOTHING in the PT-50c should have smoked that extension cord,, NOTHING,