The new upload field has 2 minor "issues" / glitches

Upload field throws an exception with short filenames

"Short" means prefix length = 1.

See stacktrace

The exception is also displayed on the UI.

Drag & Drop drop-zone must show visual change when being "targeted"

The upload field allows drag&drop.
The old version gives a visual feedback, when an item is over the drop-area. This is very helpful. If it lacks, and if one "misses" the drop zone, the browser will render the dropped item (e.g. an image) and leave the admin-central.

Please check the older versions to understand how it should look like.
See 

Also note that info.magnolia.ui.field.UploadField contains

TODO: port styling for the drop zone.