Exported gif has one frame of 2 images

[Brendan5D95]

I'm trying to get a transparent gif to export properly, however around the 14th frame of the gif the 13th frame appears behind it. It doesn't show this in the Save for Web animation preview, nor the timeline editor. What am I missing? Gif attached for reference.

[Mike Bro]

@Brendan5D95 

Take a look at layer 13...

Regards,

Mike