The other thing you might want to check, is whether the slave was installed properly. Which means, with no hydraulic pressure in the system.
The maintenance manual suggests you tie off the clutch lever before taking out the slave, to avoid the piston popping out and spilling hydraulic fluid all over, but you HAVE TO release the lever just before you reinstall the slave back in place. This is not made clear in the manual, and as a result people install the slave under pressure. This leads to crooked installations, possible damage and binding.
As long as the pushrod is not bent, simply releasing and reinstalling the slave should be enough. Like others said, check the spacer and dowel pin are in the right place. And note that the two bolts are not of equal length. Check which one goes where.