I have ordered a pentalobe screwdriver to open the back of the computer and look if I see something. If there is nothing, I go to another apple store and ask to speak to the manager.
The worse is that my machine is working completely with no issues except that the screen coating peeling away.
I'm wondering what does Apple to repair liquid damage ? What does the 1250$ price include and is this procedure warranty ?
I'd be very careful doing that, if they have resealed the screws then any and/or all of your warranty rights will be waived. The price tag suggests a new logic board. And, as per the T&C's of the purchase / warranty etc. they do withhold the right to charge you for any repairs on top of those you have may requested. The reason being, if they repair the screen but then the logic board croaks, you could technically claim again. Hence, they want to service the entire machine.
As I mentioned above, your best bet is to begin a formal complaint, and continue to escalate upwards should you not get any satisfaction in the first instance.
You can almost bet that it will be humidity that has partially triggered a sensor. And it appears to be up to you in how you defend your position in this matter.
I wouldn't go about making matters worse by cracking the seals and tampering in non user-serviceable devices. Writing a letter to the Store Manager and CC-ing the head of Apple Retail for your region is a lot quicker and less risky!
Add info (edit): It worked for me, when a botched repair happened on my last machine. I ended up almost screaming at the Store Manager in store, shop front to an audience of customers. Whilst he denied any and all responsibility. But it got no where. A day or so later, I wrote a letter detailing the fault, repair, outcome and complaint, CC'd in the head of Apple Retail UK. Within 48 hours, I was asked back to the store, they gave me a formal apology and a new machine.