Meizu m2

Recently i got Jio india sim (Unlimited internet ) and i put it in my m2 with 5.1.9.0G.I charged it with 100% and connected the hotspot with jio sim to my laptop and started ownloading some movies.At that time the phone is in locked condition.After some minutes i got 0kbps speed in download.I checked the phone and found that the phone automatically get restarted at 92% of charge condition.The hotspot got off due to that restart.May be its a bug of overload.I download the last parts using the phone in unlocked condition without bringing the screen off.Then no problem.I checked this problem again in next day.Same resulting the same.I contacted my friend who is using an m2 note having jio sim.He checked it as above and felt same problem after some time at screen lock.Is it a problem of jio network?Anybody (indians) pls try this case and help me to solve it!!!

Also anybody here can u pls tell me is there any new night mode available in new G??