When converting back to a previous version, it is usually the new element types specific to the new version that cannot be converted back.
So for example, Curtain Walls became available in AC12. If you convert an AC12 project that contains Curtain Wall elements back to AC11 format, the Curtain Wall will be missing in that file.
But since there were no such changes in AC14 regarding Master Layouts, those should convert back just fine.
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