@jdstiger could you please share with us url to your site, where we can check the issue?
@ajasra please note that YITH WooCommerce Wishlist bundle FontAwesome 4.7.0
Any inconsistency is probably due to the fact that your theme dequeues wishlist assets, and loads its own version of FontAwesome
Unfortunately, as you said, FontAwesome changed a lot with version 5.x, and also switched to a new naming standard: this is the main reason why we didn’t update library in first place
We’re planning to release new and updated FontAwesome with one of the following major releases, but I cannot give you any ETA currently