Has anyone encountered the line graph looking like a zig zag. The 2 hour reading shows alternate readings up and down by about 8 points - over and over. I am just hoping the receiver isnt faltering. I wonder - it was sitting on the floor last night( on carpet) and we had our first snow. Could it be the cold? It has been wonderfully accurate up til now. It is showing dodgy readings for the last hour! I have tried to calibrate. Her actual reading was about 2 mmols above the bottom reading. The glucose reading is quite stable - just the line graph!