This article explains the error related to mgd unable to execute the vrrpd and snmpd files.

Below is the commit error seen:

mgd: unable to execute /usr/sbin/snmpd: Authentication error
mgd: unable to execute /usr/sbin/vrrpd: Authentication error
error: configuration check-out failed

Possible reasons to get that errors:

• The above error indicates that the Junos device (Juniper switch or router) encountered an issue starting or running the SNMP daemon (snmpd) and Virtual Router Redundancy Protocol (VRRP) daemon (vrrpd). The specific error "Authentication error" usually means there is a problem with permissions, credentials, or configuration.
• There is possibility that /usr/sbin/snmpd and /usr/sbin/vrrpd binary is missing, corrupt, or has been deleted accidentally. Basically could be file system corruption. If the file system is corrupted or mounted as read-only, the daemon may not be executable.

Workaround to resolve this issue:

• Hard reboot the switch.
• If issue persists the format installation can recover the switch from corruption if any.

If issue persists then please open case with JTAC to investigate the issue further.