[Galaxy Note Pro 12.2 Q&A, Help & Troubleshooting] Eduvator:
Updated Information

I have a Galaxy NotePro 12.2 LTE (SM-P905). This problem began for me several months ago when I had to travel to another site for business and did not take my charger as I felt certain I would not be able to plug it in. I was correct. I had in the past however been able to run the tablet all the way down to 15% with no issues. This time however, the tablet began shutting down and rebooting once the battery voltage dropped below 50%. Over and over and over again it looped through to the home screen only to reboot again. I tried going into the debugging mode and using the settings there that were recommended here but no good. Eventually the pin I had set stopped working and I was locked out of the tablet altogether. Frustrated and locked in the back of a taxi still hours away from home, I went into recovery mode and tried that. No good. Of course, when I got home and plugged my tablet in everything began working again except I was still locked out. Even after the tablet was fully charged, the pin wouldn't work. I ended up re-flashing the ROM. Since that day, this tablet has gone into a reboot loop every time the battery dropped below a certain percentage. Initially, less than 50%, then 65%, then 70%, and eventually 84%. It would do it whenever I watched a video or switched between apps and between screens.

I contacted several Samsung service centers, here in the Middle East and in Frankfurt, Germany. They couldn't help. Frustrated, I rooted the tablet but still no good. I, like you, searched the internet for anything that might work. I recalibrated the battery several times. I ran battery repair several times. Nothing worked for long. I even went into recovery and cleaned the cache. That worked for a few days but always the problem came back.

Then today after my tablet rebooted again at only 84% of charge, I went looking for more answers. I found this thread and thought, I've already rooted it so the warranty's voided so what can I lose? It took less than five minutes to get the back off. Then, calling on skills in electronics I learned and used for over 20 years, I checked all the connections to be sure they were secure and reseated a couple. The battery connection was already taped down but I pressed on it just to be sure. And then I took your advice and installed a thin plastic shim under the mother board to the right of the battery connector. After re-installing the back, I turned the tablet on and checked the battery charge - 95%. I launched a video and allowed the battery to discharge. When that video was over, I checked the voltage - 91% - and launched another video. I kept launching videos until the battery charge was 46%. Then, I turned the videos off and launched my Kindle app. I switched between screens over and over again trying to make the tablet fail but thankfully, it appears the shim has worked - for now. I will check it over the next several days and see whether or not it holds. I'll follow up here if it doesn't hold.

UPDATE: It's now going on day three since I opened the back of the tablet, checked all the connections, installed the shim as suggested, and physically reseated the ribbon cable on the right (display?). Because I pressed on every connection and reseated the ribbon cable in addition to installing the shim, I cannot say which has worked so far. My experience tells me it's possible one or more connection may have come loose - especially after a year of using the tablet daily with the occasional drop or knocking off the counter. However, it's also possible the shim could have provided more support to the board at the point where the battery plugs in. One thing I can tell you definitively: my battery life has returned to what it was before this problem began. In other words, the battery no longer drains to 74% in just a few hours. It now takes pretty much all day of active use to get it to the 50% mark. And that's the point: over the past two days I have managed to get to the 50% charged point without any flickering or rebooting. I've plugged the tablet in each time it's gotten at or near the 50% point.

As for those users who have not had success with the shim, may I recommend you check EVERY connection. Press on them, re-seat them if necessary. While the issue *could* be software, I know from almost thirty years repairing electronic equipment of many types, sometimes contacts get loose or dirty and something simple as pressing on them can make all the difference in the world.