Has anyone else had someone install the wrong multiport on a Pentair Quad DE Filter?  Our home warranty company installed the wrong valve, and we hired a "more reputable" pool company to come troubleshoot and install the correct valve.  Now, after the correct multiport was installed, flow switch on the salt cell replaced, new actuator for the spa, new bulkheads, new manifolds, a few replacements of the acutal filter cartidges... there is *STILL* DE flowing back into our pool.  Any ideas of what may be happening? The "reputable" guys are telling us the filter housing is "warped", and want to replace the whole dang thing for more money... any help or advice would be appreciated!  

Our Pentair Quad DE 80 filter:  P/N 188593