So I've been hearing a beep once in awhile and I kept wondering what it was. At first I thought maybe it hit a high or low alarm for a second but my temps were never near what my alarm is set to. I was just walking by it and it beeped and it looked like it said invalid and something else but I only caught a glimpse. It completely takes the temp reading away and displays words. It does it for an individual sensor, not the whole thing. I've seen it one other time in sensor 2 and just now in sensor 6. The first time I was to far away and seen it change but thought I was seeing things bc of how far away I was but now I know I'm not. Anybody have any idea what it is? I looked through the manual and didn't see anything.