Hi,
I have the exact same issue as this Topic: https://www.8theme.com/topic/urgente-mobile-menu-not-working-correctly-on-xstore-v-9-6-1-and-core-v-5-6-1/
When you open the mobile menu, then select a dropdown option, the menu opens and then closes immediately. This issue only occurs when you use the menu from a WooCommerce category page and does not have an issue when using a normal page, blog post or category tag page.
As per the above topic, I have tried adding the CSS you mentioned, but this has made no difference.
I have tried several different browsers from mobile and all have the same issue.