Why is XMetaL authoring bridge changing resourceIDs to "all caps?"

Question

Using SDL Tridion Docs R13 and XMetaL 12 with Authoring Bridge 13.0.4115. Have not made any changes to client tools for over a year. Have not changed our XML plugin settings. 
 Suddenly when we check in DITA topics, <resourceID id="" changes to "all caps." This was not happening until about 2 weeks ago. 
 We have some resourceID CSH values that use lowercase letters in our UIs. Now they're broken when we update and check in the associated topics (and then publish). 
 As shown in the attached screen shot, the "demo" portion of the "demo16" ID that I entered remains in lowercase when saved in XMetaL. But then it changes to DEMO16 upon checkin. 
 Anyone have any ideas? Thanks! 
 Paul M.

Dave De Meyer · Answer

Hi Paul, 
 Two classic questions... 
 
 First, what has changed? Although you highlight no changes like XMetaL patches and no XML Plugin settings changes. Still would be my prime subjects 
 Second, cut the problem in smaller pieces. Use the web client (ISHCM) so you drop AuthoringBridge and XMetaL from the equation. So submit a file there and check if the plugins uppercase by also downloading the file from the web client. Or check how 'file system DITA" works in XMetaL 
 
 Best wishes, Dave

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Why is XMetaL authoring bridge changing resourceIDs to "all caps?"