I have an Action with "Image Size" immediately followed by "Save to JPG" script.
The Photoshop file has a Gradient, followed by "Image Group". I found that the saved JPG file does not include the gradient. However, if I insert a "Stop" with option to continue immediately after the "Image Size", the gradient will now be correctly included.
It seems that the "Image Size" command is not completed when the next action is executed.