Hello Vicki,

Thank you for getting in touch with us. My name is Andrea, and I'm happy to assist you today. I appreciate your patience while we've been working towards your ticket.

The effect doesn't stop; it just slows down and always lasts as long as the duration set for the slide. Its movement seems dashed when it has to move very little for a long time.

You need to set the appropriate values in the Slide -> Effects -> Ken Burns section. 

The start/stop effect cannot be set, but the zoom does not stop completely; it only slows down because it has an easing (which cannot be adjusted).

At this effect rather the combination of values of the kenburnsscale, kenburnsrotate, and duration (slide duration) matters.

I suggest you experiment with these values: leave one or two values fixed and change the rest until you get the look you like. 

Could you please give me a link to see your slider? Then, I could help you more.

You mentioned you were thinking of buying the WordPress version. If you do it, you should create your slider using the wp plugin, then export it as HTML. In this case, set the following slide transition to each slide: "103. Scaling tile in" transition. You can set this transition in the Slide -> Timing and transitions -> Slide transition section, clicking on the "Select transitions" button.

In the jQuery version, you can set the example above with this value:
transition2d: 103;