Hello!
Actually, the carousel using images as backgrounds. Please remember that the background images work independently and it is because of their nature in the HTML.
I have written below CSS code for you, please add it to the custom CSS area of theme options and let me know if you need any further help.
.mpc-wc-product .mpc-product__thumb-wrap .mpc-product__thumb{
background-size:contain !important;
}
Please also share the wp-admin details incase if you need further help.
Thank you!