Shadow artifacts, High Res Screen Capture

I am trying to create a really high resolution screen shot 11000 x 5000 however when I increase the multipler to higher values (in this case 5) to achieve that resolution I get artifacts around the edges of the shadows. At lower multipliers there are no artifacts I get nice sharp edges.

On the attached photo, the left side is using a low multipler value and the right side is using a value of 5.

The lighting is done with baked lighting with quality set to production.