New iTunes bug removing users locally-stored music library. Many users reporting that iTunes or Apple Music is deleting their music collection. The report says, if the user is signed up to iTunes or Apple Music, the software will overwrite iTunes Store version of music over locally stored music library.
Apple says in statement:
In an extremely small number of cases users have reported that music files saved on their computer were removed without their permission. We’re taking these reports seriously as we know how important music is to our customers and our teams are focused on identifying the cause. We have not been able to reproduce this issue, however, we’re releasing an update to iTunes early next week which includes additional safeguards. If a user experiences this issue they should contact AppleCare.
Apple has officially acknowledged the problem. The company will release the new update soon to fix this bug. Apple will soon release iTunes 12.4 update with minor UI tweaks.