He handled a repair for me. I recommend giving him 24 hours (at least) between messages. Let us know how things turn out.
As I suggested elsewhere, you should check to make sure the switch retaining ring is tight. By testing without the switch in the circuit, you have isolated the problem. If you are lucky, a simple tightening will fix it.
Early on, there were several lights where the body tube was too short to complete the circuit with the tail cap. I am not sure whether that was a problem with the body or tail cap. One or the other had to be replaced.
I think you already tried cleaning all threads and contacts with alcohol. After cleaning, you will need to re-lube the threads. You can also use DeoxIT on the contacts.
There is a troubleshooting thread for the BLF A6. You may want to discuss this more there.
Good luck.