When I upgraded my Samsung Galaxy Alpha from KitKat to Lollipop (Android 5.0.2) I found that the left soft-button that launches “Recent Apps” no longer functioned. I also found that I could not fill in forms in Copilot GPS and some other applications.

This was fixed by ticking

• Settings > Display > Increase Touch Sensitivity

It would seem that Lollipop reduces the screen sensitivity enough to cause unexpected faults.

— Update 2015-08-24 —

Adding my work email account to the stock mail client using Activesync causes a security policy to be applied. This seems to stop the Recent Apps button working. However I would not expect this to adversely affect data entry into other applications.