WooCommerce effecting drop down menus

A friend has asked me to add WooCommerce to their website, https://sunderlandparents.co.uk so I downloaded, installed and activated the latest version of WC and the default pages were created.

But I noticed it stopped the ‘About’ and ‘Christmas’ drop-down menus appearing when I hovered over them. So I backtracked and tested again at each stage. I removed the pages from the menu then I removed the pages altogether but still no luck. In fact it was only when I deactivated WooCommerce that the drop downs started working again but at this point no WooCommerce. It’s not because the WooCommerce pages appear under the ‘Christmas’ menu as some of the original pages appear under ‘About’ and that’s not an issue.
Any idea what options I need to be looking at to address the cause of this, it’s a right royal pain as it has never happened before. And simply activating WooCommerce causes it to happen!