Rae from Shopify here. Thanks for posting this question - I'm glad to help further with this.
Can you please share a few screenshots, or a screen recording, of how this looks from a customer's perspective? Once I have an example of how this appears, I can help look into this issue in more detail.
Also, are you using any third party apps to control product variants, or are you using the built-in variants in the Shopify admin?
Once I have the above details, I can certainly help take a deeper look into this issue.
I look forward to hearing back from you!