Shutter release button gets stuck sometimes. How to fix it?

Hi great community, I am (was?) an happy user of the olympus pen el-P2 digital camera.

I have a problem: Sometimes, After i shot a picture, the button doesn't seem to go back to the original position and remains stuck halfway.

Olympus only repairs in Italy are online and costs for this model 220€ . Not worth a penny.

Do you have any suggestion