Why do apple keep messing up?

Every time a new upgrade to the operating system is issued it messes up iMovie.

I took sometime before upgrading to El Capitan only to wish I hadn't as changing the length of any transitition is now a nightmare!

its been the same on previous upgrades, so frustrating.

will get fixed in a future update but we won't get told about it, until then I have two projects on hold!

Very annoying!