Hi, for known PostgreSQL corruption-related fixes you can check this
filtered list:
https://why-upgrade.depesz.com/show?from=12&to=18.4&keywords=corruption.
To identify problematic objects/blocks, I would first try a classic
read-through test with pg_dump dbname > /dev/null 2> errors.log, but be
careful because this can be heavy on a busy production system.