BizTalk 2013 R2 - Decision Shape not following correct logic path - biztalk

Question

Issue with an old Biz app (not designed or developed by myself).
Its orchestration receives a particular message, which is then fed into a Decision shape. If the below logic applies (as directly copy/pasted from the shapes first branch expression), it should go that route.
msg_inputCanonical.CRUD == "D" && msg_inputCanonical.DbTable == "Staff"
I can see it terminating however (by using the Orchestration Debugger) as it follows the Else branch and eventually hits a terminate shape.
I've checked the msg_inputCanonical to confirm the values being passed through (as below extracted from the Tracked Message part), and can see it matches the string condition in accordance with its mapping - CRUD = ChOp;
<DbTable>Staff</DbTable>
<ChOp>D</ChOp>
There's nothing else that I can see that's influencing this re-route, so can anyone think of any quirks that might be causing it?
Note: I've amended the WCF-SQL Stored Procedure that generates the msg_inputCanonical as prior to this it wasn't trimming any of the CRUD/DbTable values and had been leaving deadspace in.
There is also a map that uses ltrim/rtrim functoids on the ChOp property, but again - can't see what harm trimming an already trim'd field would do.
I have also tried replicating the logic in a dev environment, and it works as expected going down the correct branch when I'm passing the message through.