[systemd-devel] systemctl, unclear error msg/warning, "Refusing to accept PID outside of service control group..."

[rop]

When doing systemctl-status on an old application, we are now seeing this
error/warning:

   "systemd[1]: Refusing to accept PID outside of service control group,
acquired through unsafe symlink chain"
I tested to remove a symlink in the chain, but then got this instead:

   "New main PID xxxxx does not belong to service, and PID file is not
owned by root. Refusing."
And when trying to examine the pid-file, it wasn't even created.

In spite of these errors/warnings, it seems the application is still
working...
So I am not sure when this error started appearing,
but I suspect it has started after some RHEL OS-upgrade in the last year(s).

googling didn't turn up much, so far....

Where can I find an explanation of these messages?

What exactly is deemed "unsafe"?

And what to do about it?
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