Cut Song: Sarah's Dream Ballet called "Die Roten Stiefel" in the original Vienna production was cut in all later versions. It was replaced by "Stärker als wir sind / Das Gebet", except in the Japanese version, which is the only production so far to restore it.
The severe postponing of the Belgian production, which was caused by the producers of the show suing for more government support money and as a result putting the show (which was already in rehearsals and scheduled to open in December 2009) on hold until at least October 2010.
The Polish production ended prematurely, purportedly because license holders didn't want to jeopardize the Berlin production that was about to open some 600km further away.
License holders for the show are famed for being adverse to any changes, up to and including already-written additional songs being scrapped because they would change the rhythm of the plot. Apart from the Broadway production, the only one that got away with significant choreography changes is the Japanese one.
Thomas Borchert is pretty sick of playing Krolock, but the producers of the Vienna revival pretty much refused to even audition any other comers. So guess who got pushed into the part again?
What Could Have Been: Original announcements and promotion for the French production indicated that French pop star Dumè would play Count von Krolock; he was forced to withdraw a month before the opening due to a back injury.
Development Hell: Hello. First, there was the innumerable amount of script changes and song-cutting/adding that went on because of so many people getting involved with the project. Then, there were several technical failures that cancelled preview shows and pushed the release date back. Then, the release date had to be pushed back further, due to it originally being just after a certain 2001 American disaster. (The producers - rightfully - felt that putting on a comedy about dead people would be in poor taste.)
Executive Meddling: A key reason the Broadway version turned out the way it did was because the producer felt American audiences would reject a European pop opera out of hand (after the subgenre's heyday in the 1980s) and wanted something funny. Combined with hiring Michael Crawford for Krolock, who didn't want to repeat his work in The Phantom of the Opera and was more than fine with the comic approach,note Actually a return to form for him after the Phantom was initially a major case of Playing Against Type. the show was more or less doomed from the start; the details on the production and the differences between it and the original show are here and here.
Typecasting: Michael Crawford's intense fear of being Type Cast was the main reason Krolock was changed into such a comic character. As he put it, he didn't want to be playing "the same guy with bigger teeth".