AF-ON button very loose

My d850 AF-ON back button focus is getting pretty loose. I’m a 40+ wedding photographer and in the heat my thumb gets sticky and causes damage to it over time.

I’ve had it repaired previously but is there anything I can do to avoid having it get so loose and potentially falling off mid wedding or do I just have to look into new body’s when it’s at its worst? I don’t want to have to repair it every year.