The device type is recognized if removing then readding the device. The configuration on the device can be collected without a problem, in under 30 seconds, too. The device credential verification jobs confirm the RO and RW string are in LMS correctly. Packet captures on the server show SNMP requests and replies coming and going when deleting/readding the device via Inventory > Add / Import / Manage Devices.
Still working with TAC to investigate but was curious if anyone else is having this issue, or something similar. It's just the inventory collection that doesn't seem to work.