checkout gets stuck and cannot remove items or exit please help

[fmgsound]

hello guys! so things have been working relatively smoothly on my website, but i have noticed that when i add an item to cart and go to my checkout and try to purchase a product the checkout cart window gets stuck and wont exit or allow me to remove items from the cart... is this a glitch only on my system? I want to make sure this isnt happening to customers! A few customers have said they had trouble with checkout... what should i do?

my website is 

https://www.fmgsound.com/collections/all 

there are the products so you can see the checkout process

Thank you soo much!

-Fernando

[fmgsound]

i am encountering the issue on my phone but not on my desktop! could somone checkout from their phone and see if there is an issue adding a product to cart and then removing it or trying to exit from the page