This problem is most likely an actuation fault and not a clutch kit issue.Check the clutch fork. It may be broken or worn out.
Why does it happen?
The clutch fork's function is to disengage the clutch when changing gears which makes it susceptible to breakage and wearing. This breakage and wearing – including the thinning around the fulcrum – will start to flex/tilt resulting to change of motion ratio of the fork and to still and inconsistent pedal.
Check the clutch for signs of heavy wear and replace if required. Common types of wearing: pivot fulcrum wearing, and breakage.
Avoid installing cover assemblies with much higher clamp loads over the original equipment specification. While new components will be able to deal with more torque and horsepower, it will wear down the clutch fork causing it to crack under pressure. Subaru's original equipment design is intended for specific load and service life.
There are several reports concerning disengagement issues in Subaru vehicles. Most of these issues are not due to clutch kit failures. To verify, check the clutch fork and replace when necessary. Checking and replacing worn and damaged clutch fork will ensure excellent performance of the clutch.