In my humble opinion, your problem is not fixation. My guess is insufficient dehydration;if the water isn't removed, the wax doesn't go in. Try using  only two formalins and adding a third 100% alcohol.
OR..... if you want really great processing, try 7 parts 100% alcohol/ 3 parts xylene in the first 6 stations, then 4 xylenes and 4 paraffins. See the March 2000 Journal of Histotechnology for details or email me. We've been using it for 7 years now and have never had a poorly processed specimen. The xylene mixed with the alcohol prevents over hardening and sections are easier to cut, especially fatty specimens!

Wayne Hohn