BUG #18002: Duplicate entries of row possible even after having primary key

The following bug has been logged on the website:

Bug reference:      18002
Logged by:          Ajinkya Tankhiwale
Email address:      ajinkya.tankhiwale@tcs.com
PostgreSQL version: 14.7
Operating system:   RHEL 8.8
Description:

We migrated from 13.7 to 14.7 recently, in current data setup, we say that
duplicate records are present in table even after primary key. I see that in
the past, same issue was reported and possible solution was to run full
vacuum or re-index. We tried both, but still able to enter duplicate
records. 

This is blocker for us and would like to have solution for this as soon as
possible.