Mobile view showing huge white space on first load, fixes after refresh

Hi! I’m having a really annoying issue with my Readymag site on mobile. The first time I open the published link on my phone, there’s a huge white square/empty space underneath the actual page, so the whole site looks broken. If I refresh the page, it suddenly loads correctly and the white space is gone.

Does anyone know what causes this or how to fix it? I’ve checked the mobile layout and I honestly can’t figure out why it’s doing this. It’s driving me insane