Galaxy Note keeps turning off if not in charger

Hello gentlemen,

I've been using my galaxy note for a year with no problems. Several weeks ago, I rooted the phone and tried out a custom ROM - GalactusMod. I have since went back to stock (thru nandroid backup) and everything worked fine, until I got this issue.

My phone just keeps turning off. Usually, several seconds after startup, the screen flickers for a second or so, sometimes I lose phone reception and imminently afterwards the phone turns off. Sometimes the screen just flickers and nothing happens - but in such a case it starts flickering again in less than half a minute (and it usually turns off that time). This also happens when on airplane mode. However, the issue doesn't appear when a) the phone is in recovery mode, b) when the screen is off. c) when the phone is in charger. In all of these cases, it shows no "symptoms" even after a long time. When in charger, I can operate the phone anyhow, but I've noticed that apps from google play (or APKs) can't install. Internet otherwise works.

I'm using a stock ROM on an Exynos Abuse rooted phone. The following procedures have failed to fix the issue a)factory reset b)cache wipe c)installing a custom rom d) going back to a nandroid backup from the time it worked fine.

What should I do? I'd like to try every possibility before sending it to repair. Does the warranty apply? (I'm in EU, GT-N7000 model). If I'm to send it into warranty, how can I get rid of all indicators of there ever being a root/custom ROM?

EDIT: I unrooted the phone through ExynosAbuse. It didn't help. I also noticed that the phone reception is completely reliable when phone is in charger, but when it's on battery, it turns off frequently, mostly just seconds before the phone turns off.

Thank you in advance,

Mulenex

 

I installed a custom ROM and then restored a backup through recovery mode. Both of these procedures are, I imagine, highly battery consuming. I have a Phil Z recovery mod that shows the battery level, and one full backup restore took about 10-15 % of battery (in about 20 minutes). That seems a bit more than usual, but not outrageously so.