I see @partial = "workbar_work". When render (partial: workbar_work, ...) is not found, the _workbar_work.html.erb file. Because it is inside the work folder

$('#workbar_switch').html("<%= j render(partial: "work/#{@partial}", :locals => {exercise: @exercise@}) %>");

or

You can set @partial = "work/#{permitted_params[:partial].to_s}"

$('#workbar_switch').html("<%= j render(partial: @partial, :locals => {exercise: @exercise@}) %>");