CSS for making Avada testimonials equal height

You can force a minimum height on overall testimonials box to avoid the jumping behavior.

For that, please use a bit of css like below. You can add this css to the very top of your Theme Options -> Custom CSS area.

.fusion-testimonials {
    min-height: 500px !important;
}

You can adjust the 500 value to 600 or 700, etc. as needed.