Thanks for posting jk3. Apart from the smoke(!) it sounds very much like my problem. Till now I'd been thinking that this was just a very annoying waste of $19, but your experience sounds downright dangerous; puts things in a whole new light.
Apart from the link in humppa's post https://budgetlightforum.com/t/-/4032, several other members have posted of similar issues with the WP2 ii, and that's just here at BLF. Makes me wonder how many got sold worlwide, a sobering thought. IMO the more people who report such experiences the better. This charger got so many good reviews that I'm sure a lot of buyers will feel perfectly safe just leaving batteries on charge overnight. To be fair, they probably will be ok, but these faulty samples are out there.