pipe freezing just outside the compressor

[subzero*psia]

If the box was freezing inside, (shelves were developing ice as he said) yet the system never shut off.... (even when he manually shut the t-stat off)... I would say the t-stat contacts were arc'd closed. That could be from running too many appliances off the same circuit providing they called at the same time etc.

I don't believe that I would go any deeper "knowing" the t-stat failed to shut the system down when he turned it off, or at least not yet. The ice on the shelves does suggest his door seals are leaking also. JMHO...

By the way... I do agree with your thought on the frozen suction line though... frost on a suction line doesn't necessarily mean anything, depending on box temperature, ambient temperature and humidity level as you said.