Hi Harsha,
This is common and a very important step when designing Security on transactions.
In your scenarion it looks like t-code F-02 is talking to FB50 t-code in the backround due to which it takes the auth data for object K_PCA and is providing access to all the 3 PC.
You first need to check and break the ralationship between these 2 t-codes in TCDCOUPLES table so that F-02 does not talk and fetch the auth data for that object in the backround.
You can run a trace on on test id and see what authorization are getting checked and maintain the security accordingly.
Thanks
Uttam