I think you have fallen prey to the ‘stupid **** design’ issue with GX cranks…..
They are not preload as a poster above correctly said. Unfortunately, they rely on a little sleeve thing that sits between the axle and the inner race of the bb bearing. You might not even notice it. In my experience, what happens is that the axle gets a bit cacky and the sleeve bit wears away. It then comes apart from the plate bit that acts as a bearing seal. When this happens, the axle can wiggle in the bearing.
A fix I have bodged is to have a rubber washing machine seal or two between the sleeve/seal thing and the crank arm. That way the sleeve/seal cannot wander out.
On later models SRAM specced a wavy washer to do this ‘bulking out’ and any engineer that specifies a wavy washer is essentially admitting there is a design flaw somewhere…….