floatless fuel sending unit issue

[statenine]

Hey all, I recently finished my LS swap and have a new tank under the bed in back. I used a floatless sending unit from Tanks Inc. Everything was fine in the beginning however the other day I started it I noticed the fuel level had dropped from nearly full the night before to 1/4 tank that morning. I went for an hour drive or so around town the night before and did not really pay attention to the fuel level, so I thought ok maybe I used more gas than I thought. So I ran to the gas station to fill up and it only took about 2 gallons and it was full. The fuel level is still sitting right around 1/4 tank though. Do you think maybe my sender is defective? Or is it my gauges? I am running Dakota Digital gauges. Would there be any other reason this is happening?

Thanks