[T-Mobile LG G4] verbage:
Regarding your phone being rooted, my wife's VS986 was rooted as well. This did not even come up in conversation with the LG. Even though her VS986 was clearly out of warranty, as soon as I started to explain the symptoms I was seeing, the LG rep (without mentioning the word "bootloop") said he recognized the problem, and that they would repair it for free. In sum, at least in my experience, having the phone rooted did not make one iota of difference. I guess the takehome message is that this issue has obviously reached levels far greater than the average 5% electronics failure rate--LG recognizes it is a hardware problem, and is prepared to deal with it (even on rooted and out of warranty devices).

You said your phone does not have the bootloop issue, but I invite you to investigate it further because the bootloop issue is not strictly confined to continuously bootlooping as I tried to explain originally. What you have described completely fits within the spectrum of observed issues related to the bootloop issue. Question for you--when you turn on your phone, is it normal that it shuts off at some (whatever!) stage of booting? You said that at point you actually got into download mode, but then it failed there--is that the normal/expected reality? No, it's not, and this behavior is definitely one type of expression of the bootloop issue... And as you reported yourself, you boot seem to fail at a range of different spots, not always consistently at the same moment. If it were a software problem, wouldn't it always happen at the same stage? That it happens at different stages of the boot process suggests an external control, i.e. a hardware issue.

You asked about the freezer trick--let me roll things back a bit, and I'll get to this in a minute. The bootloop issue is supposedly related to a failed electrical connection for a component on the phone mobo, and so how far along the boot process actually gets before failing gets is related to thermal expansion of components, at least this is my guess. As I mentioned, when my wife's phone originally locked up, on trying to restart it immediately, it was completely dead, no LG logo no anything. But after letting it sit untouched for a couple hours to cool passively, the boot process would at least advance up to the LG logo, but then fail. After this, if I tried to reboot again while the phone was still warm, again, complete failure (not even reaching the LG logo) until I let it sit and cool for a while. This is all related to the freezer trick...

I read that on freezing their phones, some people were able to boot as far as the homescreen, and have a few minutes to rescue their contacts and photos before subsequent failure. So I tried that with the VS986, and was even able to get past the Verizon logo as mentioned above. But failure occurred during the optimizing apps stage, and I could never reach the homescreen. Whatever the case, this freezer trick simply works because of thermal contraction--by cooling the phone down enough, the components contract rebridging the failed electrical connection, and if it can can stay cool enough for long enough, you might actually have a few minutes to rescue things before failure.

There are some other data rescue techniques, too, and though you do not seem to be concerned about rescuing data, I mention them because they also point to this thermal issue. In particular, besides freezing, some folks have tried exactly the opposite--intense heating--and they have been able to get a few minutes of data rescue time out of their phones. This involves heating the back of the phone with a hair dryer until it is close to burning hot, and then trying to boot. This certainly works because of thermal expansion--heating the phone up so much causes everything to expand which literally forces the components back together bridging the failed electrical connection temporarily until the component heats up internally, and overcomes this extra pressure.

Another data rescue technique involves adding a spacer above the CPU to cause more force pressing down on the component to bridge the connection failure. And some people have literally ironed their CPUs in attempts to resolder things, and have had various levels of success. But in the long run, all of these attempted repairs to phones with the bootloop issue have the common characteristic of rebridging the failed component connection temporarily, and that is key here--they are only TEMPORARY. They work for anywhere from 1.) not at all to 2.) a few minutes to 3.) a few hours to 4.) a few days, but in the long run, they are temporary, and mobo replacement is needed.

Anyway, I encourage you to investigate the G4 bootloop issue a bit more before you conclude that your phone is not affected. And furthermore, in the long run, if you do conclude that it is afflicted by the bootloop issue, contact LG about it, and they will probably repair it for free. Don't fear about being out of warranty or having rooted the device--at least in my case these things did not matter!!!

---------- Post added at 11:53 AM ---------- Previous post was at 11:47 AM ----------

I have reread your description above, and now even more think you may have the bootloop issue! You wrote that you were able to get into download mode, but then it failed, and then it would not do anything. This is exactly my experience with the VS986--immediately after a failure when it was still hot, if I tried to restart it, bam, nothing, not even the LG logo. But if I let it sit around a while to cool, it then was willing to show some semblance of life. Let your phone sit around after the next failure to cool down a bit, and I bet that after that, again, you will start to see a few indications of life instead of it being completely dead. If so, this should convince you even more that this is a hardware-level issue, and not simply a matter of being able to get into download mode to reload the OS.