I have had similiar happen with a couple of my Sanwu pockets, mine are all single mode.
I have the 445 500mw, the 405 200mw and the 650 250mw.
Anyway I have had times where after charging up a battery(10440-flat top unproctected) that when screwing the tail cap back on the laser flashes for a second, then when I try to turn it on, nothing. Not even a faint dot. but I just tried swapping batteries and then it seems to work. So a suggestion for the OP would be get multiple batteries.
I think the flat tops don't make as good of a connection in some pockets. My 650 always worked NP with flat tops, however the 405 and 445 have done this weird problem that the OP posted. I tried putting a button top 10440 in and they worked. Sometimes just a diff flat top 10440 and works. So who knows. Could be the battery, or the laser contact inside for the positive end of the battery.
If swapping batteries doesn't work. then contact Sanwu. PM Podo