It looks like when we upgrade to Wordpress 5.2.1 add_theme_support('soil-jquery-cdn'); breaks. There’s a “-wp” appended to the jQuery version which results in a 404:
Yep. We experienced this. Looks like I have the same issue on all of my sites. Everything continues to work, so there must be a fallback. Removing add_theme_support('soil-jquery-cdn') removes the 404 error so perhaps and update is required to Soil?