Please check with latest version of XD 126.96.36.199
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MuthukumarDustin Rosing commented
I have seen this exact same issue with chrome - The auto-animate transition works fine in XD app. But in chrome only, and only upon the first view of that specific transition, the whole starting artboard art all fades out during the transition. If you go back within the prototype and trigger that same transition again, then it all works okay and looks just like it does in the XD app viewer.
This is with the latest version of XD on a windows 10 machine - just updated XD to last version on October 28th.