PG Bug reporting form <noreply@postgresql.org> writes:
> We've updated our database from 10.6 to 12.0 recently and we keep
> encountering an error which says that the database is entering recovery
> mode.
> ...
> In the logs the only error we see, is a segmentation fault, when replication
> tries to run.
It should be possible to collect a stack trace for the segfault,
which would greatly assist debugging this. Please see
https://wiki.postgresql.org/wiki/Generating_a_stack_trace_of_a_PostgreSQL_backend
regards, tom lane