Samba panic action mails

All of a sudden I get mails from winshare@mynethserver.local with the following contents:

The Samba 'panic action' script, /usr/share/samba/panic-action, was called for PID xxxx ().
This means there was a problem with the program, such as a segfault.
However, the executable could not be found for process xxxxx.
It may have died unexpectedly, or you may not have permission to debug the process.

What could be the cause?