I believe that there is probably nothing wrong with the controller what is happing is after charge the battery sits and the cells drop past the set voltage of the controller so when you plug back into the truck the controller does not see full battery voltage and will not set the bdi to full
what you are doing by putting the battery back on charge is juicing the cell quickly and faking out the controller for a new battery the cells in a good battery is2.1volyd per cell if your battery can't get to that after charge the gauge will not reset.what to do to check is charge the battery over night and on the morning check each cell and see if the cells are at a good battery l would bet that they are only getting to about 2..05 to 2.08 per cell. If you find out that this is the case and can get a GELX hand set you could change the setting in the controller to help with the gauge but you will still have a weak battery get back toe and l will help you.hope this helps.