error : missing chunk number 3 for toast value 14146136 in pg_toast_8895383

Hi All,

We are performing the PostgreSQL DB upgrade using pg_upgrade from 9.6 to
12.5 on the production server. The DB upgrade activity completed
successfully on prod server for all databases.

After upgraded, we are performing logical backup & vacuum full on each DB
and getting error only on 2 big tables and remaining DB working fine

*ERROR: missing chunk number 3 for toast value 14146136 in
pg_toast_8895383ERROR: missing chunk number 29 for toast value 14674367 in
pg_toast_8895400*
As we go through the various blocks as well community old issues and
performed the below steps however, still facing the same error.

REINDEX System mydb;
REINDEX table mytable;
REINDEX table pg_toast.pg_toast_8895383;
VACUUM analyze mytable;
or
VACUUM FULL ANALYZE mytable;

Also tried with drop these tables & recreate the same tables and load data
from the backup file still getting the same error.

We verified there is no data corruption on 9.6 only facing issues above
error after upgrade 12.5.

Please guide us to resolve this error.

Appreciate your help.

Thanks & Regards,
Manoj