"No such instance" on SNMP interface stats

[miken32]

We have a couple of MSM 760 boxes running 6.0.3 firmware that intermittently refuse to give us interface info via SNMP. Other MSM 760s on the same firmware work consistently as expected. Anyone else experiencing similar behaviour?

Here are two queries, a couple of minutes apart:

$ snmpwalk -v 2c -c community hostname ifdescr
IF-MIB::ifDescr No Such Instance currently exists at this OID

$ snmpwalk -v 2c -c community hostname ifdescr
IF-MIB::ifDescr.1 lo
IF-MIB::ifDescr.2 udp0
IF-MIB::ifDescr.3 eth0
IF-MIB::ifDescr.4 eth1
IF-MIB::ifDescr.5 br0

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