Vivo Y51l restarts after Starting up apps . Need Help!

Hello masters ,
I received a vivo Y51l in dead condition i repaired its dead boot via jtag box and flashed a new rom , the device now boots normally , the vivo logo is shown which leads to optimising apps and when it reaches to starting up apps it shuts down itself .
Does any1 know , how does this fault usually comes is it soft issue or hw issue or i should flash other dump and reprogramme once again ? I have tried flashing every sw ver available on the internet. So kindly help me out if its hw issue or i should work on jtag one again .
Any kinda guidance is highly appreciated TY.