[Galaxy Note 4 General] charleshking:
tldr; the thing with the oven appears to have worked, although you'd have to be stupid, desperate, or both to try it.

Much loved Galaxy Note 4 SM-N910F started to fail with freezes, reboots and so on. Looks like a phone dying of eMMC failure, according to the bulk of articles on the specific symptoms.

Happily, I'd replaced it (with a Note 10 - lovely phone, but not as revolutionary-lovely as the Note 4 was when it was new), and had had six years of happy use out of the thing. I could bin it with my head held high.

Might have a go at recovering it, though.

Attempts to factory reset failed, resulting in boot to download mode "Firmware Update Encountered An Issue" scary screen... I see. This could be a fun challenge before I bin it then!

Odin flash of Stock ROM fell over repeatedly with various fails - often with 'mmc read' and 'could not do normal boot' scary screens

Various versions and vintages of Odin all produced similar results

Un-brick seemed to work, in as much as I could then flash TWRP (https://xdaforums.com/note-4/help/samsung-galaxy-note4-sm-n910f-unbrick-t3552826)

TWRP flashing of any rom seemed to fail and fall over - generally 5-10% (guess) into the process.

Now getting bolder, tried re-partitioning, various PIT files, NAND erase, and all the forbidden things. The errors kept coming, and my 'unbrick' microSD was earning its keep.

The thing is, I really liked this phone - and I wanted it to try newer ROMs on and so forth, so I resisted the urge to chuck it in the bin. That, and finding things like using TWRP terminal mode to re-format /system and /data in different partition types, and then back to ext4, seemed to improve matters - if only temporarily - all suggested that there might be life in the old girl yet.

A couple of my searches came across articles like this and this, that suggested that the issue might have to do with failing solder joints rather than the eMMC itself and ... well then they talked about putting your phone in the oven, and I dismissed them as madness.

I mean, if putting your phone in the oven would 'reflow' dodgy solder, it would re-flow ALL the solder in the phone, right? Makes no sense. Bloody stupid.

Not going to fall for some obvious troll hoax.

So I put my phone in a 100 deg C oven for 5 mins. Took it out, and let it cool to room temperature slowly over a couple of hours.

Now

Odin can flash a whole stock ROM with success

TWRP can flash a whole non-stock ROM with success

Odin can re-flash a whole stoc... oh. Failed at around 80%. Poo.

TWRP managed a reflash, though!

Odin managed a whole stock reflash, again!

Setting up the flashed phone, though, results in freezes and boot loops. Damnit.

Another day of frustrated mucking about, hovering the thing over the bin.

OK, one more go. This time 120 deg C for 6 minutes.

This time

First and every subsequent re-flash, in Odin and TWRP, works fine.

Odin'd it back to stock, then wipe and factory reset. All fine.

Reconfig process passes without incident.

Google Play updating itself and ALL THE APPS works fine.

Setting up accounts, streaming Youtube for hours, playing games... all fine. Much more stable than it'd been in a while.

It's been a week, now, without incident.

So I thought I'd mention it.

But I still think you'd need to be an idiot to bake your phone in the hope that it'd do *anything* other than make things much worse, right?