I have the 5v PT from madvapes (not the sit n go, the basic 5v one) and the 3.7v inline batt from cignot. The batts DO go toes up quite often, I know this cos I bought spares (off cignot) and changed out one that died soon after I got it and it came back to life fine. The wires on all of them (even the thicker cable ones) are a HUGE pain and remind me of earplugs wires that you get with walkmans. I never had any luck with those either lol
However I do LOVE my PTs - and still buy them despite having mods now because they give a different vape.
(and as I type this my madvapes PT dies, oh the irony...)