Steps to reproduce:
Use the built-in template on a cisco switch which also has virtual interfaces configured.
The discovery rule under linked template Template Module EtherLike-MIB SNMPv2 will discover interfaces based on other OID than set:

Discovery rule is:

discovery[{#SNMPVALUE},1.3.6.1.2.1.10.7.2.1.19,{#IFOPERSTATUS},1.3.6.1.2.1.2.2.1.8,{#IFALIAS},1.3.6.1.2.1.31.1.1.1.18,{#IFNAME},1.3.6.1.2.1.31.1.1.1.1,{#IFDESCR},1.3.6.1.2.1.2.2.1.2]

Then #SNMPINDEX should contain vaules from the first OID, ie. 1.3.6.1.2.1.10.7.2.1.19, however, it contains values from the 1.3.6.1.2.1.31.1.1.1.1. This can be an issue when the switch has vlans which are interfaces and are reported as IFNAME but they do not have status duplex and are not reported under oid 1.3.6.1.2.1.10.7.2.1.19, in other words, the interfaces reported by 1.3.6.1.2.1.10.7.2.1.19 and by 1.3.6.1.2.1.31.1.1.1.1 are not the same. But as #SNMPVALUE is assigned to 1.3.6.1.2.1.10.7.2.1.19 #SNMPINDEX should follow this OID.
This is either a bug or missing documentation on how #SNMPINDEX is processed when discovery[] has more OIDs.