I'm writing this question having already found a solution, in order to see whether other people have encountered this problem.
I was having a problem on the back end of a site I am building in wordpress in which all the jquery scripts that I tried to load using the native wordpress handles (i.e. jquery-ui-core, jquery-ui-sortable, etc) were not loading. If I checked the state of those script handles using the wp_script_is() function, it showed that they were registered, enqueued, but not printed. At the same time my load-scripts.php file was registering an error: "jQuery not defined'.
Does anyone understand why this bug is occurring? And is this a bug in the new version of Wordpress?