Optimize User Variable Member Selector

For the past few months we have noticed it takes longer to load the Entity User Variable member selector. It's currently taking ~20 seconds to load before you can make your selection. It used to be very quick, and other dimensions are still very quick. We are not sure what is causing this delay. I tried removing the attribute dimensions we have, but that seemed to only improve load time modestly. I removed the constraint we have set (Level 0 Members) and that reduced it by a few seconds, but