XF 2.1 Tools -> Import data not working

When I am trying to import from any source (it doesn't matter which one), then it states 'No configuration necessary.' and when I click on continue I will get the following errors with a completely empty screen.

Uncaught TypeError: a.each is not a function at c.updateState (core-compiled.js?_v=2724b2d0:9) at c.init (core-compiled.js?_v=2724b2d0:9) at c (core-compiled.js?_v=2724b2d0:7) at e (core-compiled.js?_v=2724b2d0:7) at HTMLInputElement.<anonymous> (core-compiled.js?_v=2724b2d0:8) at Function.each (jquery-3.3.1.min.js?_v=2724b2d0:2) at w.fn.init.each (jquery-3.3.1.min.js?_v=2724b2d0:2) at Object.f [as initialize] (core-compiled.js?_v=2724b2d0:8) at Object.activate (core-compiled.js?_v=2724b2d0:1) at core-compiled.js?_v=2724b2d0:8

How can I solve this?