I have a new bass that seems to have an issue with the truss rod. I can adjust the neck exactly the way I want it, which is almost perfectly straight. However, the neck then slowly starts to develop more relief untill it settles at a certain point. This takes a few days to a week. The last few times I've adjusted the rod for a straight neck, it took more force then I wanted to use. Maybe it's maxed out, I don't know. But this didn't happen the first few months of owning this bass. Any ideas what's going on and how to fix this?