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Importing a .tmx file into an existing .sdltm file

I can't import any .tmx file into an existing .sdltm file.

During Import, it says that x numbers have been imported but when I do a manual search in the TM View, I can't find any of the segments imported.

My tmx files can only be imported into a newly created/empty .sdltm file. 

I'm using the latest version of Studio. The .sdltm are "upgraded".