OpenManage - WS MAN discovery stopped working

I have two instances of Open manage (2.2 and 2.3) running (one prod and one dev, both in the same subnet managing different vlans). Mid week last week, both ceased recognizing nearly 200 Dell servers/iDRACS; all devices are now 'unknown' status after being fine for many weeks/months. 

All iDRACs are discovered using WS MAN only. I've performed the following steps to rectify this to no avail;  

1. per http://en.community.dell.com/techcenter/systems-management/f/4494/t/19512525, timeout on the ICMP and WSMan discovery pages

that the WSMAN  creds were working; all tests passed with the tool. 

Deleted and re-added the vlans and performed a re-discovery. 

4. unticked/stopped using the 'Secure' mode for discovery

While this sounds to me like a possible change in my environment, is there a way to better determine what is going on through OME itself? The logs aren't particularly useful, and the fact that WS MAN tests work directly from the troubleshooting tool and not OME itself is a bit odd.