Question [Q] [HELP] SoD keep bugging me after all my efforts

Hi guys!

I've been experiencing some SoD (Sleep of Death) episodes about 3 weeks ago. I've been searching for a solution ever since.
Specifications:
Phone: Samsung Galaxy S i9000;
ROM: currently stock 2.3.4 - I9000XXJWQ

Problem:
-phone keeps shutting down by itself, regardless of what I'm doing. Sometimes, when I reboot, the battery level shows 4-14%. After a second reboot, the battery shows the normal level of 60-70% (the level that was shown when the shut down occur)
-drastic drops on battery levels (screenshot attached - I've been experiencing some more drastic drops than that)

Tried, but no results:
1. I tried other ROMs (6 of them), from JB to KK (Cyanogen McKay SlimBin etc. found on xda) +wipes
2. I tried other battery - still my phone shuts down itself
3. Flash stock kernel and ROM with Odin
4. Battery recalibration didn't work either- I don't know if I made it correct. Read here a post about it and I understand that wiping batterystats.bin dose nothing but clearing the history of the battery consumption. Also, I think that flashing stock ROM took care of wiping that file so no need for calibration (correct me if I'm wrong please). Also, I think trying another battery excluded the possibility of a faulty one.
5. Checked the connection between the phone and the battery. Also I've wrapped the battery in a paper to make sure it didn't move. The phone shutting down even when it stud still on the desk made me think it was not the problem.
6. Wi-Fi setting about sleep: From "Never" to "When screen of"

Q: What do I do next?
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