My name is Lilith, I'm on the Social Care team at Shopify.
With that in mind, I would highly recommend downloading a fresh new copy of the same theme from the Theme Store and checking if you get the same issue. Ensure that you don't add any code or change any code before you test the new theme for the issue.
If you don't have the issue on the brand new copy, this could mean you had some code in your other theme that was causing this interference.
Let me know how you do with the information above! I'm happy to answer any questions you think of as you work on your business.