How to clean a sticky Magic Trackpad click?
My Magic Trackpad 1 also lost its ability to unclick and I had to lift it up to get it to release. I tried various cleaning fixes but none worked for me. It seemed that there was no spring-back action left in the magicpad. I use the pad a lot in photoshop with lots of clicking and dragging so I guessed the spring had finally just worn out. However I found a solution on this website.

https://www.ifixit.com/Guide/Magic+Trackpad+Click+Adjustment/6171 

It was more than I wanted to try, but I really need my magic pad to work as I had a big project on the go. The fix works well and I added little adjustment to the procedure. In step 3 where the adjustment screw is pointed out in the photo, the bar it is set in is also the spring that provides the un-clicking action of the pad. I gave the whole bar a gentle pull upwards, away from the pad, this put some spring back into the trackpad. The Magic trackpad now works perfectly again.

I also used 2 rubber self-sticking bumpers to replace the feet. These bumpers are often used on the back of picture frames to protect walls or under trays to to prevent scratching tables. The size I got were 8mil and fit perfectly. The added advantage to putting them on first is than you fine tune the screw adjustments you make to the trackpad before replacing the white back to the trackpad. This video shows put the bumpers on. 

https://www.youtube.com/watch?v=WmO_G7Ct9k8

Final word of advice, gently warm the white back of the trackpad before removing it. A hair dryer works well and I just laid mine in the sun for awhile.