MacBook Air - Wakeup time long and getting longer

Hi, I have a 2013 Macbook Air 13'' (A1466) running Mac OS Sierra which has wakeup issues. I spilled some creamy, sugary coffee on it about 1.5 years ago, after switching it off right away, letting liquid leak out and doing the right things it magically survived. So I assume corrosion might be finally taking its toll.

Everything works perfectly on the mac, except for when I close the lid and lid stays closed until the mac goes to deep sleep (couple of hours?). When I open the lid again it takes very long to wake up. The wakeup time has also been increasing in the last couple of months (used to be a few seconds, now it is about 7 minutes).

The things I tried are:

1. Running Apple diagnostics (nothing wrong, battery and power connection is also fine)

2. SMC / PRAM reset

3. Removing everything and reinstalling a fresh Mac OS Sierra (there is now nothing non-native installed on the mac)

I just ordered some pentalobe screwdrivers to open it up to see if I observe anything strange. Is there anything else I can try in the meanwhile?