On the auditdistd server (FreeBSD 11.3) these errors appear.
The problem only occurs with 12.x clients, 11.x clients do not have this issue.
Oct 14 14:07:16 audit01 auditdistd: [client01] (receiver) Unable to receive request header: Operation timed out.
Oct 14 14:07:16 audit01 auditdistd: [client01] (receiver) Worker process exited ungracefully (pid=21079, exitcode=75).
On the client (FreeBSd 12.1), we see:
Oct 14 14:07:16 client01 auditdistd: Sandbox process exited ungracefully (pid=65308, exitcode=75).
Yes, we know these two examples are on past-EOL versions.
We originally thought this was related to https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=240762 but that seems to not be the case.
Given the past-EOL versions, I will test this with a 12.1 server & both 12.1 and 11.4 clients