Transparrent pixels after trim

Hi Creatives,

I'm really stuck with this one...

I have artwork that I have scaled down to make a repeating fabric pattern.  As elements fall off the edges of the canvas I have needed to use 'trim'  so the pattern repeats seamlessly at the smaller size.   I am then left with a  single line of transparent pixels that are slightly lighter than the artwork.

I can sometimes add a rectangle layer at the back in the base colour but this doesn't often work as there are many shades of colour in the patterns.  

I have attached some files to show what I'm seeing (zoomed in and also how it leaves a faint line on the artwork)

I have about another 30 files to scale and then export as a jpeg so would really love a solution.