I think Richard is probably right, although on one fermentation a few weeks back, I had a similar low Tilt reading throughout fermentation. I had put the Tilt in and racked chilled wort on top of it and a good slurry of harvested yeast; long story short - the Tilt somehow got stuck under the Brewbucket's dip tube, which was in the downward curved position, so it held the Tilt for the full time of the fermentation. I just assumed that it was a battery going dead or something, so I didn't figure it out until I racked it (closed transfer) and then opened the lid to find it lodged under the dip tube in an unusual way and figuring out that it just wasn't free floating. Strange things can certainly happen, but usually, they are nothing to worry about! Even so, they can be temporarily confounding.