A am very plumbing illiterate. I have a bath/shower with a drain attached to a lever. The lever is located about a foot above the drain in the tub. For some reason, the lever will not stay in the down position very well. I can hold it down or try to jam it by pushing it on an angle. There is no clogs in the drain, so there is nothing pushing up on the drain to cause the lever not to stay down. Is there a way to get the lever to stay down?