This article explains about the syslog message 'IFFPC: 'IFD QUEUE stats' & IFFPC: 'IFD QUEUE stats' on the FPC found on the MX router.

The below error messages reveal that there is a discrepancy between the kernel and the PFE with regard to the physical interfaces (IFDs) that are believed to be active. 

Nov 1 01:08:22 MX480_RE0 fpc4 IFFPC: 'IFD QUEUE stats' (opcode 117) failed 

Nov 1 01:08:22 MX480_RE0 kernel: if_pfe: Error 5 (Invalid) on IF command 117 (IFD queue stats)

Nov 1 01:08:22 MX480_RE0 kernel: if_pfe: Error 5 (Invalid) on IF command 117 (IFD queue stats)

Nov 1 01:08:22 MX480_RE0 kernel: if_pfe: Error 1 (Unknown) on IF command 138 (IFD chassis queue stats)

Nov 1 01:08:22 MX480_RE0 fpc4 ifd 262; Null queue get stats vector 

Nov 1 01:08:22 MX480_RE0 fpc4 IFFPC: 'IFD QUEUE stats' (opcode 117) failed 

Nov 1 01:08:23 MX480_RE0 fpc4 IFRT: 'IFD get Chassis Queue stats' (opcode 138) failed 

In this specific case, the IFD that is being referenced is located on a Physical Interface Card (PIC) that was taken offline.

The error messages are triggered when the command 'show interfaces statistics' is executed. The exact root cause of these messages is currently unknown.

The above messages are not service affecting and it won't generate Major/minor errors.

These errors just logs because there is discrepancy between the kernel and the PFE with regard to the physical interfaces (IFDs) that are believed to be active. 

Workaround is to reboot the FPC during the MW time.

KB8239 [juniper.net]: https://supportportal.juniper.net/s/article/M-EX-QFX-Interpreting-the-meaning-of-IFD-related-error-messages?language=en_US