How do I get next/prev post featured image source link?

Hello, I’m using Featured Video Plus in my theme, and I’m trying to add images to my Post navigation Next & Previous buttons. I’ve achieved getting those images using the standard get image function, but the Featured Video Plus plugin replaces the post_thumbnail automatically, so I’m wondering if anyone knows how to just grab the NExt/Prev post featured image source link instead.

I have got this to work with my category & archive pages by grabbing the featured image source link, but having a little trouble with the Post Navigation function.