[Sprint  Galaxy Note 4 Q&A, Help & Troubleshooting] samep:
Doesn't sound like you're having all the issues posted by the OP if stock was fine for a week and you can Odin successfully and have no issue until installing a custom ROM.

You replaced your battery and stopped using older ones? That camera issue was either a bad battery or incompatible camera in a custom ROM, IMO.

The stock ROM that worked fine for a week and the custom ROM that spontaneously reboots, which were they? Most likely, you're limited to what mods you can apply. In that condition, were you using stock or custom kernel? Kernel tweaker or none? Am I wrong to conclude your issue is the custom ROM and possibly custom setups?

Could you describe the random reboots? I've personally experienced a scenario where a ROM may run fine until user factory resets and ItsOn tries to install its bootstrapper but cannot with custom kernel or missing resources. It's persistent though, got a prompt to reboot with no issue or reason given when all seems well except the prompt to reboot that may actually become unexpected reboot if notification it's disabled and ignored. Some have found its best to factory reset and wipe internal memory when this happens and then install custom ROM cleanly. [MENTION=309990]freeza[/MENTION] even added a line in script to delete /carrier/ItsOn folder and contents when that was identified as the issue when not wiping internal memory when completing ItsOn bootstrapper prior to installing custom ROM. I believe that works in that scenario but it highlights a need for user to follow OP install to prevent that in ROMs that omit that line in scripts. This could be a disconnect where phone isn't tested but deemed compatible with Sprint and data patch.

But kernel tweaks can cause issues with random reboots. The kernel I use works well with interactive governor but the rest are not as stable or fluid. I can under volt but only 25 or 30 mV and I limit over clocking to 2 steps above stock, no further (goal is stability without hurting battery with reasonable gains). You should consider that each processor has already been profiled to run within a specific volt to frequency table based on its ability so there's little room to limit with no adverse effects. Major steps can have adverse effects. Over clocking should also be given the same respect. We're already maximizing performance near threshold of stability. Think small steps, rather than large. Using the developer recommended kernel tweaking app is paramount for success as well.

Swapping kernels repeatedly may also leave your phone in an incompatible state so that even restoring boot.img partition to stock isn't helping. The reason is the modules the kernel uses. Developers will modify the contents of /system/lib/modules. Hopefully that's done in a compatible way but each custom flash over pre-existing custom setup may not be ideal but works best flashed over stock modules. If developer has done thorough testing, maybe the adverse effects have minimized but you can see where not having the phone for testing may impact users. Restoring boot.img only leaves the modules in unintended modification, especially for stock boot.img

Just a few examples of why a custom ROM may not be as compatible as stock for some users or carrier subscribers. You should mention the ones not being so compatible when comparing to stock as well as knowing that custom kernel tweaks and applications may not work as well on all ROMs.

There is a possibility you've chosen an incompatible ROM; ported ROMs may be nearly fully functional but have issues like you described. There's many workarounds posted in this forum that admittedly aren't fully functional; much effort has been shared by a few that have given much effort to find most compatible ROM but I think we'll get more stable support out of the box for Sprint version on Sprint from [MENTION=1503720]tx_dbs_tx[/MENTION] soon enough if your phone holds up- the OP describes an all too common failure with eMMC failure on Note 4. Sprint compatibility is tougher due its network and porting ROMs is tedious and may not work fully on phones not on hand for test.