I have 6 switches that inventory is failing for. They do run the 12.2(33)SXI3 software but I have the CSCtb16925-1.0 patch installed. I've tried to increase the SNMP timeout for the devices but they still fail.
You did not properly increase the SNMP timeout. Go to RME > Devices > Device Management > RME Devices, and edit the attributes of the device in question. Perform an inline edit. Click on the device name, then change the existing SNMP timeout value to 10. Then save your changes, and apply them on the previous screen. Then inventory collection should work.