Yosemite random reboots on macbook mid 2012

Question

Well I've read thoroughly all the posts related to this kind of issue and it seems it affects a wide range of devices. Either mac minis or 2011 macbooks and so on.
I would like to explain my experience and ask for any advice available. I am experienced with computers and OS's, even though I would not call myself an expert, but as an engineer I possess a certain amount of knowledge. So there it goes.
TL;DR at the bottom
Macbook pro mid 2012 13". Default 4gb memory installed, I added a Samsung EVO 830 SSD in 2012 when I bought it, never had any problems with it.
After a couple of weeks after upgrading to yosemite (november '14) I started noticing the macbook resting on login screen after a reboot. No crash report, no message visible of any reason. As I was installing some special software to do some work related to a lab I was working at the time, I thought it was software related. MS Word and Excel often crashed and I had a couple of problems with other programs. Then it started doing it while I was working, so I decided to check things out. The system freezed for some seconds - 1-2 minutes and proceeded to reboot. Sometimes a hard reset had to be performed.
I decided to perform different installations with different options in order to identify the problem:
Reinstall Yosemite from recovery mode: same result, random reboot, no specific app in use, either Xcode, Safari, or just resting idle with just finder.
Format disk and install yosemite applying time machine backup: same result, random reboot, no specific app, and so on.
Format disk and clean install, manually installing the same main software installed previously: same result, random freezes and reboots.
Format disk and clean install, manually installing essential apps (mac app store only): same result, exactly the same result.
Always with the latest OS version available, and with TRIM enabled and disabled, to discard issues with it. PRAM and SMC resets all along.
During all the testing, the console has not shown any crash report or kernel panic related to the event. After every reboot, console would not show anything special before the boot_time line.
After looking for solutions on different forums, I noticed a pattern on some cases that implied a wake on lan or a handoff, or wifi issue. I tested on different networks, disabled and enabled all options commented, with no effect.
Entering
syslog -k Sender kernel -k Message CSeq 'n Cause: -' | tail | awk '/:/{$4=""; print}'
on terminal 90% of the time returned errors -128, and some -112 or -2, but they would not be logged to every freeze, just some of them. By the time the
As they may indicate a hardware error, I decided to proceed with the warranty.I bought the Applecare extension when I bought the computer (expiring this summer) so I talked to Applecare about the issue. As there is not an official Apple Store in my town they pointed me to an ASP in my city. They noted all the issues I commented above, gave me a case number to deliver to the ASP so they would have all the information.
I brought the computer to the ASP, gave them the case number (which they totally ignored, the employee seemed oblivious to what a "case number" was) and expected them to find the error. As I noticed the freeze could be sometimes forced via waking up the laptop, I made them a demo. I had ran already the apple hardware test and any hardware tests I was aware of. Etrecheck came out without issues or anything worth mentioning, so I thought they might have specific apple tools to identify hardware error.
They told me they could not find any error on the computer, but that they found errors in the SSD, swapped it with one of theirs to test and no issues found. Good, I thought, at least they found the issue even though all tests run on the SSD by me did not show any trace of it. They charged me 25€ for the service as the SSD was not part of the original computer. As I had been experiencing issues for some time I did not care. I asked them for some kind of report to check the error to provide to the SSD manufacturer, Samsung, as they offer 3-year warranty on SSD's and it had not yet expired. The report said "errors in disk", plain and simple, I asked to talk to the technician for extra info, but he could not remember if it was "corrupted sectors" or something else.
Contacted Samsung, sent my SSD in, and in 4 days I had a new (refurb maybe) SSD same model same size at my door. During those 4 days I reinstalled my old  original HDD. As it had a few miles on it (using it as external disk) it was really slow and sometimes it would freeze but the whole system was always dragging, so it could be also failing. Worth mentioning that when swapping disks I noticed the ASP had messed up the position of the small screws on the back of the computer. They did not seem to know there are 4 shouldered screws and 3 regular ones.
I put the new or refurb SSD in, clean install and do some testings. First day everything ok. Proceed to install software. Seems ok. After a couple of days the first freeze and reboot appears. After a couple of PRAM and SMC zaps, events seem to be reduced to a minimum. Even though the system is not completely stable, and I am not quite satisfied with the uncertainty of the freezes (in the middle of a presentation is not the best moment to have one), as it's freezing 1-3 times per week I consider it reasonable.
Time goes on, freezes start to appear again. Sometimes while booting, sometimes on login screen, sometimes on heavy usage sometimes on idle. I still follow all threads related to similar issues, in case a fix appears. All sleep / wake / wifi on - off on sleep tests have been performed.
Now the issue seems to be reduced to two kind of events: random freezes and reboots, and errors while booting. None, and I mean zero of the reboots or freezes has ever had a .crash or any system diagnostic reports related to the hour or even date when the freezes took place. EVER.
While booting, it crashes and I have to hard reset 2-3 times. When freezing, 30% of the time it does not reboot, and gets warmer than idle state but cooler than under heavy load.
I usually zap pram and smc and then it boots normally. But I should not have to be doing that every time I turn it on.
I know its a long post, but it's something I have been following for 5 months now. It's not that I am unaware of different options to solve it. Zapping seems to be the way to go, but still the random freezes interrupt workflow and provoke loss of data.
TL;DR: same freeze and reboots as other people. No discrete GPU to relate it to. Default memory installed, SSD model working on 10.8 and 10.9 with zero issues. All software installation combinations tested. ZERO crash reports on console related to the hour or date of the events. Shutdown causes negative codes, ASP cannot find the issue.
Considering bringing it to Genius Bar, but undermines the purpose of a ASP and if they got the same tools they will not find the issue either.
Appelcare expires in June. Any options I am unaware of? I would relate it to the specific model of SSD under Yosemite if I was the only one experiencing freezes and reboots, which I am not.
Thanks you

Answer 1

Boot into Safe Mode. If the problem ceases then you need to remove Virtual Box and the software that installed com.bluecoat.kext.bckd 4.4.1f20. If this does not fix the problem then make a Genius Appointment and take it in for service.