Fluke 1507 insulation tester with battery leakage damage

[Khaveer]

Hello.
I've recently picked up a very cheap and very dead Fluke 1507. Initially the meter was totally dead. There were absolutely no signs of life after turning it on. After disassembling it I've noticed minor signs of battery leakage around the microcontroller. I've neutralised the corrosion using some vinegar and cleaned the board with IPA. After letting it dry for a couple of hours I've tried turning the meter on again and it started giving some signs of life. The LCD is now kinda working. All segments are repeatedly turning on and off, like some sort of a test pattern. I've recorded a slow-mo video of the fault to see what's happening: https://drive.google.com/file/d/1BAP1jEUVatYUXfK5caP5T5A6ZVn15oGH/view?usp=sharing. It appears to be some sort of a test mode but I have no idea what's causing it.

I've tried looking for any obvious issues but I couldn't find any. One thing I found interesting is the negative voltage rail powering U14. It is generated by U12 (area marked in red), but then it goes thru R95 which drops it down to -1.2V. Could anyone verify what voltage is supposed to be at TP6? Another thing I noticed it that the range switch contacts do not make contact on top and bottom pads at the same time. I've attached a picture showing the range switch contacts on top and bottom in the same switch position. The bottom contacts are not aligned properly. I'm not sure if it's an issue or if it's designed like that.

Update:
The issue was caused by corrosion hiding under the microcontroller. Decoldering the micro, cleaning the board and resoldering it solved the issue. Unfortunately the voltage measurements are now offset by +0.3V but it appears that it's still within specification