PANIC: could not flush dirty data: Cannot allocate memory

Hi all!

We have a setup with a master and plenty of logical replication slaves.
Master and slaves are 12.12-1.pgdg22.04+1 runnning on Ubuntu 22.04.
SELECT pg_size_pretty( pg_database_size('regdns') ); is from 25GB (fresh
installed slave) to 42GB (probably bloat)

Replication slaves VMs have between 22G and 48G RAM, most have 48G RAM.

We are using:
maintenance_work_mem = 128MB
work_mem = 64MB

and VMs with 48G RAM:
effective_cache_size = 8192MB
shared_buffers = 6144MB

and VMs with 22G RAM:
effective_cache_size = 4096MB
shared_buffers = 2048MB

On several servers we see the error message: PANIC: could not flush
dirty data: Cannot allocate memory

Unfortunately I do not find any reference to this kind of error. Can you
please describe what happens here in detail? Is it related to server
memory? Or our memory settings? I am not so surprised that it happens
with the 22G RAM VM. It is not happening on our 32G RAM VMs. But it also
happens on some of the 48G RAM VMs which should have plenty of RAM
available:
# free -h
total used free shared buff/cache
available
Mem: 47Gi 9Gi 1.2Gi 6.1Gi 35Gi
30Gi
Swap: 7.8Gi 3.0Gi 4.9Gi

Of course I could upgrade all our VMs and then wait and see if it solved
the problem. But I would like to understand what is happening here
before spending $$$.

Thanks
Klaus