Rumour: Early cut of Justice League deemed “unwatchable”, ending reportedly changed

A report from 'Batman on Film' is stating the reason why there have been extensive reshoots for 'Justice League' is because early cuts have been deemed 'unwatchable'. While these reports have yet to be substantiated, the site did originally report that the reshoots would take place throughout June, July and into August, which has proven to be the case.

There also reports that Joss Whedon will be changing the ending to the film (potential spoilers are the source).