Why is this happening to my Gnexus?

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http://forum.xda-developers.com – Hey fellow gnex community! I recently left stock rom due to freezes and random reboots. I've tried out various rom and kernel combinations this week such as xylon/AK, Purity/AK, AOKP/franco/lean, CM10.1/trinity/franco, Rasbean/trinity, PA/lean/franco/trinity/AK and Xenon. The problem is they all freeze and reboot constantly after 2 minutes of use. I never changed the kernel settings and this is only happening on 4.2.1 roms. My favorite rom/kernel combo would be purity/AK, Xylon/AK but they freeze, wifi disconnects and never connects back and reboots constantly. So the question is why (HowTos)