2003 civic manual with good then bad then good again clutch pedal

We have a low trim level 2003 Civic DX coupe with manual transmission. We have changed the master and slave cylinder and thoroughly bled the system. Clutch worked fine for several months. Step son hit a pallet on the freeway and limped home. Now sometimes pedal is dead and other times the pedal feels great. Drove it a week ago and clutch worked nice except i do feel it starting to slip in 3rd gear. I brought it home and parked it. The next day I stat it and no pedal. I got in just now and started it and let it run about 4-5 minutes in neutral. I pulled the pedal up off the floor with my hand and walla i have clutch pedal again. What would cause a pedal to go and and forth of being dead and then good again please?