Genos is top notch and like stated above they stand by their stuff. Its pretty much satisfaction guarented.
That said however, I had the same problems with the mag plug from them. I think it was called the Super Plug or something along that lines. Worked the first time then leaked after the next change. Could never get it to stop, short of using RTV to seal it. I went back to a stock plug for a while with no problems and now use one of the two piece systems that they sell with the plug and the hose that threads into it to let the oil out. No problems with the new one.
The Super Plug that I had was from about 4 years ago, so they may have updated it.
Hope this helps
J-