index lookup not working

[llamafilm]

I have 2 Barco cinema projectors of slightly different models, that both use the same MIB. I'm trying to use lookups to apply the fanSpeedName as a label to each fanSpeed metric. This works fine on one projector, but not on the other.

This is my config:

  barco_projector:
    walk:
      - 1.3.6.1.4.1.12612.220.11.4.2.1.3.1.2 # fanSpeed
    lookups:
    - source_indexes: [fanSpeedIndex]
      lookup: fanSpeedName
      drop_source_indexes: false

The good one looks like this in the scrape:

fanSpeed{fanSpeedIndex="1",fanSpeedName="Blue formatter fan speed"} 5598

The bad one can't find the label:

fanSpeed{fanSpeedIndex="2",fanSpeedName=""} 4041

SnmpB shows that the good device is missing values for the index field:

While the bad device does include numbers in that field:

This is the opposite of how I expected it to behave. Why does this work when the index numbers are missing?

MIB

[llamafilm]

Here's another weird thing with this MIB. Using a different OID 1.3.6.1.4.1.12612.220.11.2.2.4.8.1.2, again the "working" projector is lacking index numbers and the scrape works fine:

lampRunTime{lampRunTimeIndex="1"} 1389
lampRunTime{lampRunTimeIndex="2"} 0
lampRunTime{lampRunTimeIndex="3"} 0
lampRunTime{lampRunTimeIndex="4"} 0
lampRunTime{lampRunTimeIndex="5"} 0

The other projector does have index numbers and the lampRunTime metrics is completely missing in the scrape.

[SuperQ]

Seems like a device bug. I don't know what SnmpB is, but if you could use net-snmp snmpwalk command line tool, it might shed some light on the data. Providing a walk output for the two devices for the whole table (1.3.6.1.4.1.12612.220.11.4.2.1.3).

[llamafilm]

Here's the snmpwalk output from both.
bad.txt
good.txt

SnmpB is an old tool for looking at MIBs and discovering what info is available on new devices. It's a bit clunky but I haven't found anything better. https://sourceforge.net/projects/snmpb/