Workaround:
1. Go to File > Options > File Types in Trados Studio
1.a. If this modification needs to be done for a template, go to File > Setup > Project Templates > select the template > Edit... > File Types
2. Untick the filter XML 2: OASIS DITA 1.3 Compliant and click OK
3. Re-create the project in Trados Studio
The XML: OASIS DITA 1.3 Compliant (XML: DITA 1.2 v 1.2.0.0) filter will open the file successfully.
![User-added image](/servlet/rtaImage?eid=ka54X000000oZ1a&feoid=00N600000030BY7&refid=0EM4X000002DFY0)