This is Rae from Shopify. Thanks for letting us know about this.
I'd love to take a closer look at these buttons to help determine why this is happening. Do you have a screen recording that shows the buttons moving slowly or not working at all? If so, feel free to share this in a reply to me here.
Can you also please confirm the name of the theme you're using? You can find this information in your Shopify admin under 'Online store > Themes > Current theme'. If you're using a Shopify-developed theme, our team can help look into this further. However, if you're using a third-party theme instead, it's best to reach out to your theme developer about this for more assistance. You can contact them by following these steps.
In the meantime though, some local troubleshooting may also help resolve this, so I recommend giving these steps a try:
If you're still running into troubles with the buttons after completing these steps, please let me know.
I hope to hear back from you soon!
Thanks for following up with these details.
Did you have a chance to take a screen recording of this happening? If so, please feel free to send this recording in a reply to me here, along with your store's URL. That way, I can check out your cart page from my end, and take a closer look into this.