You could also try putting an ammeter in line with the main battery (with no solar or USB connected) to monitor the current of the board during use. When it’s sleeping, you should see a current of about 0.6mA for your configuration. If you measure a sleeping current above 1mA, then something is probably wrong, either the board isn’t properly sleeping, or something is drawing more power than it should. Have you tried swapping or kist removing the microSD card? Some cards brands use more power in a sleeping Mayfly than others. And sometimes old cards that once were good will start to go bad and use more power than normal. And on rare occasions, the pins of the microSD card socket (either the optional vertical or the horizontal on-board socket) will get bent and allow for a phantom current draw. So monitoring the sleeping Mayfly current with no memory card can be a useful tool to locate the source of the issue, as well as removing any external sensors and the cell board, all one at a time, to locate anything using an unusual amount of power during idle or sleep mode.