Pocketchange

The other day I got my multi function valve stuck on backwash. I took it apart, cleaned it out and replaced it with a new handle assembly. Before I turned the pump back on it switched between functions easily. After turning the pump back on it immediately was more difficult to change functions and less than 15 minutes later the handle was stuck in position. I took it apart again, cleaned out the inside (there was small amounts of sand under the assembly but nothing else). I put the handle assembly back in and the same thing occurred. Is it the sand that is causing the valve to get stuck? Should there be ABSOLUTELY NO sand in the area where the multi function valve is? Any and all help is greatly appreciated...right now I can't backwash my filter... it's stuck on filter unless I disassemble it AGAIN!