I noticed that the right arm (drive side) of the Shimano Deore FC-M591-S Hollowtech II is getting loose. The right side has the axis attached to it as shown in the image.
When I take off the left arm (non-drive side) I can see the axis moving up and down within the frame. I tried tightening the connection with the crank lid tool which helps somewhat. The set is from April 2011.