Currently, the 'eachchange' event is implemented as a simple jQuery plugin. It has some advanced architecture allowing it to be used with jQuery.fn.on in some situations, but this is not very reliable, usually one should call jQuery.fn.eachchange instead.
Instead of having this as a simple plugin, it should use the jQuery special event API which I have stumbled upon a while ago. It is documented here:
http://benalman.com/news/2010/03/jquery-special-events/
NOTE: currently the eachchange event logic is in the DataValues extension since it is also used in the valueview widgets. It might move again so I have filed the bug here as some of the Wikidata/Wikibase related extensions are making use of it.
Version: unspecified
Severity: normal