I've accually figured it out. It not "just me" per se. G&W's Fair is different from most other arieals. Good to see some other ppl who have been playing him longer accually miss it as well occasitionally, but i've figured out why.
Its a mixtures of timing and muscle memory mixup. G&W is my third string char. i play falco and Doc first and second. these two characters are similar in that thier Nair's and Bairs are far more effective attack than thier Fair's so the Fair is not a commonly used attack in both characters. In fact, i have never shffl'd a doc Fair because its wind up time is horrendous.
However, with G&W its pretty much impossible to play him without the Fair but let me get to the point. an empty L-canceled Fair works perfectly just like any other char's. However, upon contact with a enemy, there is lag in the move itself. Hitting something with the Fair causes a lag in landing time which completely throws off your L-cancel muscle memory. This explains why i was able to l-cancel his Dair but not his Fair properly. You accually have to wait slightly longer to hit L than in an empty Fair because the lag makes you hit it to soon and thus miss that cancel. thats why i found it difficult at first to shffl the attack perfectly because i didnt realize the lag from the accual contact.
i realize now that the same thing happens with Doc's Fair but i wouldnt know that because the fair is a horrible move to shffl with doc.
well yea anyway that explains the timing mishaps. i those who have been playing G&W longer either have long ago adjusted or dont notice anymore. But it is different so its not just me. ^__^