I got the Marshmallow upgrade pushed to my phone on Friday. Since then the phone started locking up fairly regularly where I have to pull the battery to use it. I've done 2 different resets of the phone now and I haven't had it stay functional for even 5 minutes at a time since then. Any suggestions? How possible is it to downgrade the software version back to Lollipop and how would I go about doing that if it is possible?