On the tank with the issue i used a ni200 for tc at 42j on 490f. It should be within the limits of the ipv3. Do you see something I don't?
On the tank with the nickle, do you ever clean the 510 pin or on the mod ?
I would watch that 510 on that ipv3, they have had several customers that theirs came loose, but the big no for me would be to rely on the usb to charge my dual battery's correctly, 42w should give you
absolutely 0 voltage lag on fresh'ish married batterys...................
Maybe time to start saving for a new mod ?