s6 edge 925t power drain when off after water damage repair

sm-g925p recovered from water damage, cleaned board and lcd with isopropyl 99% and toothbrush, then ultrasonic cleaner, then isopropyl again.

Put in new battery. Also tried new housing/mid frame to make sure it wasn't the power button. Also tried a soak in isopropyl for 3 days.

Motherboard came back from totally dead but now there is a significant power drain when powered off! Like from 90% to 60% in 2 hours, while powered off. It will drain all the way to 0 overnight.

I haven't seen this before and looking for troubleshooting tips on SPECIFICALLY how and where to check for shorts and specific areas of the motherboard to check out under magnification.

I have heard of using "freezing spray" and then looking for which areas get hot first, but don't have any experience with this....any suggestions on a specific "freezing spray" product or supplier?

I have looked the whole motherboard over under 10x and do not notice any obvious areas of corrosion or darker discoloration, etc

Any help very greatly appreciated!!