Digitizer damage or logic board - which is more likely?

Hi all,

I have an LGUS997 G6+, which was recently water damaged. Initially the screen was not working at all, but after removing corrosion from the display connector and a few other spots with 99% isopropyl alcohol, the display now works fine, but the touch input is still not working.

I'd say about 85% of the time, there's no response to touch, or there is a response but it's too brief to actually trigger any UI elements. About 5% of the time it works correctly, and the remaining 10%, touching the screen triggers sort of ghost touches - the device recognises the input but in a different part of the screen, often in multiple different spots at once, with no consistent pattern. I haven't seen any true ghost touches, i.e. input being recognised when there's no actual touch.

My intuition is that these particular symptoms point more towards the digitizer being damaged than the logic board, although I know the only way to find out for sure is to replace the parts. So I have two questions:

1. In your experience, am I right to think the digitizer is more likely to be at fault, or is it just as likely to be the logic board?
2. Is it safe to immerse the screen assembly in isopropyl? I have seen advice not to do this with iPhones because the alcohol will damage a coating on the screen, but I don't know if that would also apply to this device.

Thanks for reading, any other suggestions also gratefully accepted.