Hi @simonphemp,
Sorry to hear about the trouble with this. Typically the problem you described is caused by a conflict from a third-party theme or plugin.
To find the cause, I would recommend setting up a staging site and running two tests. If you don’t already have a staging site set up, check with your hosting company as many offer this as part of their packages. Otherwise, you can use a free plugin such as WP Staging to set one up.
For the first test, you’ll want to change your theme to the default Twenty Seventeen or Storefront theme. Check to see if the problem is resolved. If it is, make sure your theme is up to date and then contact it’s developer to have them correct the issue with their code.
If that test doesn’t help, next disable all plugins except for WooCommerce and PayPal by Braintree and test again. If that resolves the problem you can slow reactivate your plugins while you test until the issue returns.
Once you’ve found the cause of the conflict (plugin or theme), make sure it’s up to date and then contact it’s developer to have correct the issue.
If that doesn’t help, we’ll need to run some further tests on your staging site. At that point please go to WooCommerce.com and log into to create a new ticket with our team.