RD, there are is one and maybe two free upgrades to the G21.
One is a re-cut extractor slot and a new extractor. I had to send my slide in for that.
They other, if it applied to the 21 (it applied to several, if not all, of my Glocks) was a replacement Trigger Mechanism Housing which also included a reshaped ejector.
Perhaps either one might be your problem.
They wanted me to send the frame in to have the Trigger Mech. Housing replaced but I told them, on the phone, that I was familiar with the process and would do it myself. They sent the part. I didn't want to go through the expense of shipping a "firearm" commercially.
Give them a call with your serial number handy and see if yours need the upgrade.
Good luck.