Only seems to happen in 1st gear. Shifting from 1-2, put the clutch to the floor to shift and it doesn't disengage. It holds the revs for 2-3 seconds, dropping 100-200RPMs, then completely disengages at around 1700RPM. If I shift above 3000RPM this does not happen. Also, if I only disengage the clutch to right after the point of disengagement, and not to the floor, this does not occur.

I was originally thinking pressure plate in the clutch, but that'd affect all gears, not just 1-2, and the rest are fine seemingly fine. It goes into gear without any problems once it disengages.

Clutch fluid level is normal and there's no apparent leaking from the slave or master cylinders.

Help!