[unclenunzie]

Before you send it in degrease the striker channel with polymer safe gun scrubber or similar. No lubricants in the striker channel on these guns. See if dry fire works better afterwards.

You mentioned retainer spring rubbing on the trigger bar. Do you mean the trigger bar spring (#14)? If so you can put a tiny dab of synthetic grease there. And also a tiny dab where the trigger bar and trigger are retained by the trigger spacer (#11).

In general the Kahr trigger pulls should be very smooth, non-gritty and non-stacking with a clean break. If you try the above and it still is poor I'd send it in.