Unwanted white lines and grey borders in & around my repeating pattern tiles when I scale/resize?

Hi everyone,

I am having trouble with my repeating patterns that I make in the Object>Pattern>Make.

I need to be able to make a surface pattern in one size and then scale it bigger and smaller for different uses.

I have tried two different ways and each gets me a different problem.

If I edit the original scale in the area of editing pattern swatches, and "save a copy" as a new swatch in a different scale, I get white vertical and horizontal lines inside my swatch (see the picture).

If I just use the original swatch to fill a rectangle and then have another identical sized rectangle underneath it with the desired background colour, and then scale them and the art board by say 50%, I end up with a grey border around the tile. Then if I try to use my tile as a repeating pattern it has a thin uneven border that is also repeated.

i have fiddled with so many settings and making sure everything is done in whole pixels and the the X and Y axis in the top left corner are set to 0 for everything and art board matches etc etc but I still get one or both of these problems.

I have been left having to recreate my patterns from scratch every time I need to change scale- but this is often impossible due to how many elements I have used and resized etc.