96 Ford Exp Sport Hard To Shift

Hello, My son has a 96 ford explorer sport 6 cyl. with 100,000 miles on it. Just had the clutch t/o bearing and slave & tranny fluid replaced about 2 months ago. When car is cold it shifts very good, once car warms up a little it begin to shift hard. Can't seem to get it in gear w/o pushing hard or wiggling. I checked the clutch reservoir fluid seems ok. Just seems like the clutch is not fully disengaging??? Anything i can try? thanks for the help.