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The following bug has been logged on the website:

Bug reference:      17485
Logged by:          Peter Slavov
Email address:      pet.slavov@gmail.com
PostgreSQL version: 14.3
Operating system:   Ubuntu 20.04
Description:        

I a noticed a problem in our production database when rebuilding the primary
key index. The database has a lot of INSERTS and UPDATES when this is
happening. I was able to reproduce this on PostgreSQL 14.1/2/3 locally on
docker instance and on AWS EC2.
Here is how you can reproduce:
- Load table `test2` from this file containing the table structure and small
testing dataset:
   
https://drive.google.com/file/d/1vCqKOda3IIrHmWDzNNJaDQfCb5eQA_D2/view?usp=sharing
- Start inserting and updating in this table using pgbench:
    SHELL: pgbench -r -T 1000 -f test.sql -c 50 -j 50 receiptbank
    test.sql file:
https://drive.google.com/file/d/1mdduGqu1XcDg01iwSysF7szrIlCKUJQT/view?usp=sharing
- Reindex the PRIMARY KEY (it is possible to have to repeat this 2-3 times):

    SQL: REINDEX INDEX CONCURRENTLY test2_pkey
- Check index with `amcheck` extension for errors:
    SQL: select bt_index_check(index => c.oid, heapallindexed => true) from
pg_class c where oid = 'test2_pkey'::regclass;
    SQL result for me: 
      ERROR:  heap tuple (13134,18) from table "test2" lacks matching index
tuple within index "test2_pkey"
- Check for missing records in the index:
    SQL: WITH missing_check AS ( 
              SELECT t1.*, t1.ctid, EXISTS(SELECT 1 FROM test2 t2 WHERE
t2.id = t1.id) AS flag 
            FROM test2 t1)
            SELECT id, ctid 
            FROM missing_check 
            WHERE flag = false;
    Result for me was several records found ONLY with the sequential
scan...

This problem is possibly related to BUG #17478

Thanks for the help,
Peter Slavov