Possibilities: 1. Object blocking clutch pedal. Sounds dumb but it happens way more than it should. 2. Bad brake/clutch fluid in hydraulic clutch systems. Similarly, stuck, worn, corroded cable in cabled clutch systems. 3. Bad oil in transmission. 4. Worn/bad clutch plate or bearings. 5. Bad master/slave cylinder.
Hello bro, I have some issues with shifting too. I think I have the same gearbox as you have (kwb 6 speed) on my 2009 Scirocco. I feel difference when shifting while motor is on (first and second feel a bit stiff) and when motor is off shifting is effortless. I don't think I should feel a difference and I consider replacing clutch. What do you think? I can send a video and show how shifting looks like