First thing to do is bleed the system. Even the smallest of air bubbles in the system will cause problems such as occasional disengagement difficulty. Be sure the brake fluid in the clutch reservoir is topped off correctly with the black stopper installed.
Otherwise if bleeding has no effect, it's usually the slave gone bad. Even brand new ones, especially cheap aftermarket replacements, can be bad out of the box and not give the movement needed to allow smooth, flawless disengagement 100% of the time.
If it turns out to be a cracked/flexing bracket or worn/busted bushings, you got lucky.
The only solution I have found thus far is to use only the correct Ford OE parts when replacing any part of the hydraulic system, master, slave, bearing, etc. I'm sure a good brand clutch with a quality pressure plate helps too.
Going aftermarket, or using "compatible" parts from other years of Explorers, or Ranger parts, despite them fitting, seems to affect the clutch operation quite negatively. The exception might be using newer years parts on an older system, such as the later 93-97 master/slave designs on a 91-92, or the 98-01 systems on a 93-97. Usually this requires replacement of the ENTIRE hydraulic system and clutch/bearing/plate assembly due to fit differences.
