Transmission and clutch problems during diesel particulate filter regeneration.

Check if there's any visible obstruction or debris around the clutch pedal that might be causing it to stick. If the pedal mechanism seems clear, it could be an issue with the clutch master or slave cylinder. Inspect for any leaks or damage in these components. If you're unsure, it's best to have a mechanic take a look, as this can affect driving safety. Let me know how it goes or if you have more questions!