Clutch holds to floor while driving

My car clutch sets. Disc, bearing and plate, and slave cylinder has been changed recently. After that, all working okay, pulling, shifting, etc, all okay. No complaints.

However, just about 3,000 km of driving since the above replacements were made, the car suddenly failed to engaged any gear while driving. The clutch pedal all the way goes to floor and never return back. I have to manually return to its original position and then pressed again repeated. However, it still sticks to the floor and never return back.

I was driving and all of sudden the issue happens. Stuck in traffic and was pull over to roadside with traffic police help.

Wait for some time, and yes, it come to engaged and disengaged again. All okay. But, the problems arise intermittently!

There is no physical leakage, damage or low fluids in the system. All okay.
(It used to happen when clutch is used often ie in traffic jams, clutch engaged and disengaged frequently, just in 10 minutes or so. However, no issues with pulling power and no clutch slippages, temperature, coolant all okay.)