Why does making another artboard affect the gradient in a different one?

Have you tried applying a Layer Mask or Vector Mask to the Gradient Layer before adding the new Artboard? 

It's still one big cavas, artboards are just special groups "masking" an area of the canvas.. Is this the "new" gradient tool or the "classic" legacy gradient? Please post a screenshot of the layers panel with the artboard expanded and the layers in the artboard visible.

Hey, @Justin00421. Welcome to the Photoshop Community. We'll need more info to help you figure this out. Please share screenshots, or a video of this behavior & the system info from Photoshop Help > System info > Copy & paste into a text document > upload & attach here.

If you can, please share a sample PSD that is just one step away (Duplicate/New artboard) from when the issue appears. This will help greatly.

Are you using Gradient tool, or Gradient Adjustment Layer? If you use Gradient tool, try changing to Classic Mode from the toolbar and check if the issue exists.

Awaiting to hear from you. Thanks!
Sameer K

(Use '@mention' to tag me when you reply)