Could be a bad battery if there is a cut off switch. If lever rests on button then the linkage and spring are not all good. Examine and Adjust. The lever would have to actually push button in, to contact hot lug on starter, for a possible battery drain/draw, not just resting/touching.
If lever rests on button, it's wrong. So start with that in mind. That needs to be fixed regardless. The lever return spring may seem "strong" but it's not or needs one end moved. (just a note: there are two return springs involved, one is on the button).
Have battery load tested with a true carbon pile tester.
As Chip says, can you tell us where and how the cut off is wired, maybe a pic? That's very important for us to understand because if it does cut battery off completely, then for sure it's a bad battery or charging system or battery cables/connections. Can not be a parasitic draw.
Last edited by bartamos; 03/10/2025 2:33 AM. Reason: clarification/grammar