The usual suspects? Pressure and/or angle?
Some say an injector needs pressure, but I strongly disagree. I never use pressure and get some my best shaves from injectors. They may feel like a cartridge razor in the hand and tempt you to use pressure. Don't.
I find the angle used for an injector very intuitive, but then again I have used them a lot. You can get a harsh shave with the wrong angle though. Put the razor on the back of your hand or on your arm with the blade parallel to your skin. Tilt the handle until the blade starts to cut hair. That's about the angle you use. If you tilt the handle much more the shave can be harsh if memory serves me well. (Same procedure I use to check the angle for any razor I don't know yet).
Then again the blade may be buggered. Make sure the blade doesn't scrape past the blade stops at the front of the razor head when injecting. That's how you can ruin a blade with a Schick injector. I assume that's the same for PAL injectors.
Billy?