[Galaxy Note 4 General] DaKillaz98:
EXPLANATION THREAD:

TL;DR: There is no TL;DR, I expect anyone who wants to take this seriously to read all of this. If you want to skim, don't bother posting replies.

DISCLAIMER: ANY THING POSTED BELOW WON'T FOR SURE FIX OR EVEN EXTEND YOUR PHONE'S LIFETIME. IT IS NOT FOR SURE THOUGH, IT MAY EVEN SHORTEN YOUR PHONE'S LIFESPAN EVEN SHORTER.

I would like to start out by saying thanks to all the other people with eMMC read issues and their testing to help find out what works and what doesn't works. I can't list you all, but I would like to say thanks anyways.

What is this about? [You may be asking me as you are reading this.]

This is about the issues with Note 4's starting to lag, crash, stutter, and downright refuse to boot.

.

Why bother with the thread, here to rub it in their faces that your phone works?

No. In fact, my phone also has these issues, that's why I bothered researching into it.

Well, then? What's the point?

Be quiet and I will get to that.

Note 4's have started having eMMC issues quite recently, the whole shebang probably started around April of this year. (Not quite sure, just an estimate.) This results in storage lags that are really bad, to the phone crashing entirely, to the phone even failing to boot system, or even read the bootloader. The problem is that this is affecting anyone who owns a Note 4, be it rooted or not rooted, someone who has been on stock the whole time to someone who flashes every other day. There isn't even any signs to look out for before it starts happening, it just happens.

Can I fix it using [XXXXXXX] Rom or Software Fix?

No. At least from what we all have seen, you can't fix this with software, it is a Hardware issue.

But wait, NYiCoN made a thread about how he fixed his issue with software.

Personally, everyone's case can be slightly different, I have tried his method, but it didn't work for me sadly. I am not saying his method doesn't have a chance of working, go ahead and try it if you haven't. I linked his thread just in case. If it works for you, great, rejoice in your working phone, if not, keep reading. I will cover some other things to try.

Some of the causes to the problem that people are thinking of, I have compiled together. I wanted to point some of the more major ones out first. These responses are my testing, not anyone else's.

● Battery being an issue? (People tend to believe this because a battery pull can fix boot issues.)

I have bought multiple batteries off of Amazon from Anker and Samsung, and haven't seen a difference with different batteries.

● Rom being an issue? (I and others, including this thread by forbidinjustice have been observing this.)

I myself have found that a stock rom does improve if not entirely fix all the issues. This may have something to do with the kernel. My recommendation: Try wiping the entire NAND with a re-partition PIT file, a stock image of Marshmallow or Lollipop, your choice, and Nand erase all selected in ODIN, I will explain this process later.

● Kernel being an issue? (Maybe something to do with power management?)

I have found that most eMMC issues happen to me on roms with custom kernels, like CM, or device ports. I have also observed that my eMMC only crashes when it goes from a low-power state to high-power state too quickly. Which would explain why it can crash during doze, or when the phone isn't using the eMMC too heavily.

● SIM and/or SD Card (SD bus doing something to eMMC chip? Not an expert with storage types. Forgive me.)

I haven't found my phone to be any more or less stable with my SD Card and SIM Card both in. This honestly has left me drawing blanks.

There are way more speculations to the problem, but those are the major ones to pay attention to. But now, onto bigger and better things to do just in case your phone hasn't died yet. Things to do first will be on the second post.