XD Prototype animations not working fully

Hi some of the XD animation is behaving a bit funky.  A couple of hte animations I am trying to do in prototype are defaulting to dissolve.  Cant work out why this is and cant seem to find any logic to it.  ie, all the animation on a art board will work except one  - all a bit random.  I found a previous comment back in Jan with same uissue and followed the workaround/fix bit it didn't do the trick (including restarting).  anyone else having this problem and/or know how to resolve.  Much appreciated.  Thanks.