Every time my ETA gets close to 0 it jumps back up. When I first checked it today I was at 47 minutes. It jumped from there to 1hr 18 when I reentered the cockpit. A couple minutes later it went back to 1:18. It got down to 7 then went to 47, and now it got to 1 minute and jumped back up to 29. Can anyone tell me why this is going on and is there anything I can do?