I'm new to upright bass (on both electric and upright I'm self taught) so please excuse my ignorance. I've noticed that when I playing (depending on what surface) my end-pin seems to slide across the floor leaving me to stop playing and adjust. Is it a mistake on my part or is it the surface I'm playing on; perhaps just a problem with the end-pin? If so, is there any way to fix this? Thanks a lot.