Paying a penalty for a license when it's already paid!?

I am writing this as I am highly frustrated that the traffic department is penalizing me for my license disc that is still currently valid untill December 2025 but I've had to pay a R1400 penalty fee for a second disc and feel this is highly unfair.

I was not notified that I need to pay since the car was transferred into my name and why was the previous owner not refunded then for her payment if I'm being penalized.

If I get stopped at a road block my car is legally valid and I can't get a fine unyet I'm being penalized of R1400.