2008 Hyundai Santa Fe Sport - Broken fuel gauge

My 2008 Hyundai Santa Fe with only 64,000 miles, recently developed an issue with the fuel gauge. After filling the tank, I soon noticed that my fuel gauge registered nearly empty after driving only 15 miles or so. A few days and several miles later, the fuel gauge still registered empty. I thought perhaps I had a fuel leak so I topped it off and the needle moved to a quarter tank. After some research, I found that this fuel gauge issue is common with the Santa Fe and replacement of the two fuel sending units could cost upwards of $500. Undaunted, I thought I would try to fix the problem by disconnecting a battery terminal and then reconnecting it shortly thereafter. I thought perhaps rebooting the onboard computer might correct my problem. Well, it worked. The gauge registered correctly–for about a month. Then, the gauge began to malfunction again. So I once again disconnected the battery and the problem was instantly corrected. What’s going on here?