Seems like it is missing the mobile-specific CSS rule for the compare price div, this can be fixed by writing a new mobile-specific rule, send me your store URL to make sure and fix it immediately.
I have a good knowledge in the LIQUID code that Shopify stores are built with and HTML, CSS, javascript, and API, hence I can fix this without affecting the existing design and its functions. I have worked with many famous themes and know my way around the theme code