I personally haven’t modified the example map, but I have made a copy to use as a testing ground for new items and assets and ever since doing so, my copy of the UT editor example map loads and an error dialog pops up showing the following errors:
Info Failed to load /Game/RestrictedAssets/Audio/SoundClassesAndMixes/PSM_AnnouncerMix.PSM_AnnouncerMix Referenced by Announcer_Mix
Error Failed import for SoundMix /Game/RestrictedAssets/Audio/SoundClassesAndMixes/Announcer_Mix.Announcer_Mix [redirection] in /Game/RestrictedAssets/Audio/SoundClassesAndMixes/Announcer
Error /Game/RestrictedAssets/Audio/SoundClassesAndMixes/Announcer : Can’t find file for asset. /Game/RestrictedAssets/Audio/SoundClassesAndMixes/PSM_AnnouncerMix
Error /Game/RestrictedAssets/Audio/SoundClassesAndMixes/Announcer_Mix : Can’t find file for asset. /Game/RestrictedAssets/Audio/SoundClassesAndMixes/PSM_AnnouncerMix