I noticed that after upgrading snmp from 5.9.4 to 5.9.5.2 that cacti
stopped being able to retrieve data from snmp devices.

I think this could be https://github.com/net-snmp/net-snmp/issues/1055

I ended up haivng to disable php's snmp module to force cacti to use
net-snmp cli tools instead of php-snmp to get things to work again.