ERROR: XX000: cache lookup failed for type 75083631

Hi there,

I'm having an issue with dropping a view as shown below:

DROP VIEW access_group_view;
ERROR: XX000: cache lookup failed for type 75083631
LOCATION: format_type_internal, format_type.c:152

I've also checked the source code here, which :
https://doxygen.postgresql.org/format__type_8c_source.html

I've tried to clear the cache as mentioned in some other thread on
community using option with number 3 from here:
https://www.cyberithub.com/drop-flush-clear-cache-memory-ram-in-linux/
-> Didn't help

We are running postgresql in a docker container.
PostgreSQL 9.6.12 on x86_64-pc-linux-musl, compiled by gcc (Alpine 8.3.0)
8.3.0, 64-bit

This is an old instance, but I would like to figure out what caused it
going forward and ideally how to fix it. We've upgraded in the latest
version to 13.1 also planning to upgrade to 14.2 in a few days.

Ideas or what info to provide?