July update!!! o_O
did u check if mobile data is activated for sim 2 under data usage option?
dang.. I thought it was the same problem like mine... mine was like sim2 data is always active even if I set cellular data sim1.. which I think happens in any stock android phone running 7.1+ after initial setup and need to turn off the data from data usage(cuz everytime i flash a custom rom on my secondary handset i had to do it everytime).. So maybe ur's one is some kind of bug I think :(