Why would an outbound WMS bin have inventory available to be committed to a new Sales Order? WMS documentation is light, and I'm tearing through system rules and all available info, but there's very little insight.

Check to see if there are any Credit Memos created off of an Invoice, we had this same issue and we found out that if you create a Credit Memo from an Invoice, the system puts the Items back into the Outbound Staging bin they were in when they were shipped.

At first, I wasn't sure, but you might be on to something, thanks for the new lead!