Welcome to EnviroDIY, a community for do-it-yourself environmental science and monitoring. EnviroDIY is part of 
I am also having a similar issue with the MB7989 with MB7955 and EnviroDIY Mayfly. My sensor was deployed for four days, and when I went back to check on it and swap out an SD card, when it turned back on, it would only read a distance of 7389, regardless of the actual distance. I am also interested in any ideas as to how to fix this issue.
For reference, my sensor is mounted in an Agri Drain water level control structure with a v-notch weir to ultimately record flow in gallons per minute discharging from a pond.
