Squeaky Retina MacBook Pro upon pressure to bottom-right corner

This believe this is normal. I have experienced the same in my unibody non-retina MBP.

I carefully studied the back cover for wear marks. Then I took a close look at the logic board without touching it.

• On the whole logic board you'll find tiny elastic sticks. They can be pushed a little. These sticks hold the aluminum bottom off the logic board.
• I did not take any chances, therefore I applied insulating tape on every place of the aluminum bottom that the sticks can contact. Also I did not want to open the cover multiple times :)
• Apply the tape again as it easily wears out.

Now the MBP does not make any of the previous mechanic noises anymore.😊

This is what the back cover looked like when I was done.