I have done further testing on an instance running the Jenkins master branch and plugins reasonably up to date. I have not managed to find drag & drop errors on job config, but I did find them on Global Tool Configuration.

My findings testing the Git configuration (see video):

• Testing on the Git tools hetero-list component, drag & drop only fails when there's an repeatable element that contains form entries.
• It works fine when only draggable with minimum markup are present on the hetero-list (only have header, help area and remove button). Removing the form fields seems to fix the issue.
• I think the result is the same for the JDK tool configuration.

Hope the explanation is understandable, I can try to rephrase everything. Video dowloadable on
https://drive.google.com/file/d/1DFkH_-XQe6J47ngYkAH730Foe8ausmY9/view?usp=sharing . It was too big to upload to the issue tracker.

I'm looking at this and so far it seems that the best option is to straight up replace the drag & drop library. Trying https://github.com/SortableJS right now. 

Doing a deep search across the jenkins ecosystem it seems it can be easily done, as the use of the dragdrop.js file is limited to hetero-list.js and repeatable.js.

Thoughts on this? cc Oleg Nenashev, Gavin Mogan

There may be issues with these tests, last updated on 2009. 

• https://github.com/jenkinsci/htmlunit/blob/master/src/test/java/com/gargoylesoftware/htmlunit/libraries/YuiTest.java

• https://github.com/jenkinsci/htmlunit/blob/master/src/test/resources/yui/2.3.0/tests/dragdrop.html

Does anyone have any insight on these tests?

that htmlunit is not used, we use upstream so ignore it or get someone to archive it

I have determined that the best approach is to replace the drag & drop library with a better, more supported one. I chose SortableJS as mentioned in a previous comment. The PR to replace the drag & drop implementation and fix this issue is https://github.com/jenkinsci/jenkins/pull/5177.