This article describes an issue where the "FIFO errors" counter in the 'show interfaces extensive' output increments on SRX4100 and SRX4200.

The "FIFO errors" count under the MAC statistics section increments.

> show interfaces xe-0/0/0 extensive
Physical interface: xe-0/0/0, Enabled, Physical link is Up
  Interface index: 131, SNMP ifIndex: 509, Generation: 134
  Description: N/A
  Link-level type: Ethernet, MTU: 1514, MRU: 1522, LAN-PHY mode,
  Link-mode: Full-duplex, Speed: 10Gbps, BPDU Error: None,
  Loop Detect PDU Error: None, Ethernet-Switching Error: None,
  MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled,
  Flow control: Disabled
  Device flags   : Present Running
  Interface flags: SNMP-Traps Internal: 0x4000
  Link flags     : None
  CoS queues     : 8 supported, 8 maximum usable queues
  Hold-times     : Up 0 ms, Down 0 ms
...
  Traffic statistics:
   Input  bytes  :     4279309869361705           1368306944 bps
   Output bytes  :     1607372218414624            587296584 bps
   Input  packets:        6330356263449               268805 pps
   Output packets:        4491546780629               216731 pps
  Dropped traffic statistics due to STP State:
   Input  bytes  :                    0
   Output bytes  :                    0
   Input  packets:                    0
   Output packets:                    0
  Input errors:
    Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0,
    L3 incompletes: 0, L2 channel errors: 0, L2 mismatch timeouts: 0,
    FIFO errors: 0, Resource errors: 0
  Output errors:
    Carrier transitions: 0, Errors: 0, Drops: 0, Collisions: 0, Aged packets: 0,
    FIFO errors: 0, HS link CRC errors: 0, MTU errors: 0, Resource errors: 0
...
  MAC statistics:                      Receive         Transmit
    Total octets              4375935688411386 1682193119842629
    Total packets                6330375987883    4491546746868
    Unicast packets                          0    4491546746868
    Broadcast packets                        0                0
    Multicast packets                        0                0
    CRC/Align errors                         0                0
    FIFO errors                          38275                0

The increment in FIFO errors is caused by rx_priority0_dropped events at the NIC level.
The rx_priority0_dropped counter indicates that packets classified as Traffic Class 0 (Priority 0, typically default traffic) were discarded because the NIC's internal receive buffer (Hardware Rx Buffer) was full.
These drops occur at the hardware level before the software can fetch and process the packets.
This behavior is typically triggered by a transient burst of traffic arriving at the SRX interface.
As long as this count does not continue to increase consistently, it does not indicate a hardware failure and can be safely disregarded
To confirm this, you can check the NIC statistics and verify if the rx_priority#_dropped count matches the FIFO errors seen in the CLI.

> request pfe execute target node0.fpc0 command "show nic queue-stats port 0" timeout 0 | no-more

###### NIC extended statistics for port 0  #########
####################################################
rx_good_packets: 9237520479431
tx_good_packets: 7416087579679
rx_good_bytes: 6034701930319808
tx_good_bytes: 3690542648300461
rx_missed_errors: 38275
...
rx_priority0_dropped: 38275
rx_priority1_dropped: 0
rx_priority2_dropped: 0
rx_priority3_dropped: 0
rx_priority4_dropped: 0
rx_priority5_dropped: 0
rx_priority6_dropped: 0
rx_priority7_dropped: 0