Losing records in PostgreSQL 9.6

Hi,
thanks for your help.

My team is using Postgres 9.6.10 for an on-premise application (we are
planing on upgrading to a newer Postgres version). Our application comes
with Postgres running in a docker container with its data stored in a
docker volume. Our software uses pg_dump / pg_restore to backup and restore
the database.

Now we got a ticket from a customer where their database is missing rows
from a table. There are 971 consecutive rows missing from the beginning of
the table. The missing rows were inserted first. We find it also strange,
that all the other tables don’t seem to be affected at all. It appears that
there is only data loss in this single table.
Unfortunately, we don’t have access to the original database anymore and
need to find out what happened through the backups the customer provides.
We have one backup right after they installed and initially configured the
application, which seems complete. Then there is another backup 10 months
later where the first 971 rows are already missing in this one table.

If we exclude a manual deletion, which the customer denies, we are
wondering if it’s possible that Postgres 9.6 could lose some of its data
through a storage or memory error and would create a “successful” pg_dump
with only partial data? Is such a behaviour even thinkable with Postgres?

Do you have an idea what else could cause this issue?

These are our dump and restore commands:
pg_dump -Fc --no-acl --no-owner -U acme -h 127.0.0.1 acme > acme.dump
pg_restore -d acme -n public -U acme -h 127.0.0.1 --jobs=4 acme.dump

We use just a single db user to access the database and we don’t use RLS.

Thank you.

Best regards,
Andreas