Now I understand what @JaneScanlan was asking about in a related post. This means there are business rules being set in the UI object (uh oh) and they are different than what's in the business object. Steve Malmgren's blood would boil over stuff like this.
What's going on is when you enter the Ending Item in the UI it is not a doing SetValue command (they must've done that on purpose because of this very issue!). However one must do a SetValue for the bus object (V/I, scripting, BOI, etc) and that triggers dictionary validation (IOW they must've been thinking it's okay if V/I loses because nobody imports into this file).
For me in Providex.dde the EndingItemCode field is key 000503000003
Prolly it's the same for you but not guaranteeing that (you can step thru the DDF trail to find the correct DDE key).
So if you pull that up in DFDM, you'll see Field 14 = ITEMCODE
That is called dictionary class validation (as opposed to Field 20 which dict external validation).
It effectively means this field is validated against CI_Item, So you could backup Providex.dde and blank this field out, then run Activate() function to make change flow into the physical IM_DeleteChange M4T file
That would solve your Renumber problem (but please test it!). However it would break something else. If you're importing in Merges you NEED this validation to exist.
They should've created separate fields as in:
EndingItemCodeRenumber
EndingItemCodeMerge
But that would mean changes in the UI and business logic.
Poor marks to the 4.40 Design Team for this one.