But Kevin he also said he got so many posts about loose wire that he checked and I can only assume from the rest of this second post he tighten the wire at the converter and then he had 13.6vdc and then it disappeared again.
The suggested hook up for his converter had a auto reset breaker an the battery disconnect, your suggestion is a good one and correct but when he messed with the lug something made contact and worked for awhile and then failed again. And in the trouble shooting instructions from WFCO, the first thing they direct you to do is disconnect the wire from the converter to the distribution panel. That would also a credence to your theory but read my thoughts below.
I think the converter is bad, maybe it is converting as it should but I think there is a high resistance open at the lug. Most of the wire lugs in converters are riveted to the PC boards and they do become loose.
He might have had 13.6vdc at the lug but if there was a very high resistance there may have been enough current flow to operate a meter but not a ceiling light or TV or radio.
Those things do happen.