Kelsey Hayes disc brake locking up?

I have the Kelsey Hayes unassisted discs on my 68 Barracuda and have experienced the right front brake locking up occasionally. It seems to happen mostly the first time I brake, it doesn`t take a lot of effort to make it lock up, and goes away after I`ve used the brakes once or twice. Does anybody have any ideas what this could be? Has anybody else experienced this?