I recently upgraded OS to 10.11.6 on my 2009 Mac Pro and have had problems with my Apple magic trackpad. It seems to intermittently drop and recover connection and also appears to lag in response to input. Often it will respond in a jerky way that causes me to overshoot or undershoot my target and it's hard to select things. Sometimes I lose the cursor. All of these symptoms are probably related. Are there known problems with 10.11.6 and Apple trackpad? I am using a usb bluetooth device as the built-in bluetooth is broken and have had no prior problems with bluetooth. Apple bt keyboard seems to be working fine. I am thinking this must be an OS bug, as bluetooth works fine for other devices (keyboard and wacom tablet). My plan is to wait things out until bug is fixed and if necessary revert to a wired MS mouse that works perfectly on this machine. Interestingly, the trackpad problem is very intermittent and it can work fine for a while and then start to get funky. Anyone else experience this or similar problem?