A crash occurs when scrubbing the matinee slider with a 'Sound Wave' that has 'Subtitles' enabled.
You need to enable 'Subtitles' within the settings of the asset.
Tested issue in 4.7.6 and did not occur. Marked as regression.
1. Create a new Matinee actor.
2. Add a 'Sound Wave' file by pressing enter on the 'Sound Track'
3. Enable subtitles within the 'Sound Wave' asset.
4. Scrub the Matinee slider until crash occurs.
UE4Editor_Engine!UWorld::GetAudioTimeSeconds() world.cpp:3332
UE4Editor_Engine!USoundWave::HandleStart() soundwave.cpp:498
UE4Editor_Engine!USoundWave::Parse() soundwave.cpp:541
UE4Editor_Engine!FActiveSound::UpdateWaveInstances() activesound.cpp:223
UE4Editor_Engine!FAudioDevice::GetSortedActiveWaveInstances() audiodevice.cpp:1670
UE4Editor_Engine!FAudioDevice::Update() audiodevice.cpp:1895
UE4Editor_Engine!FAudioDeviceManager::UpdateActiveAudioDevices() audiodevicemanager.cpp:263
UE4Editor_UnrealEd!UEditorEngine::Tick() editorengine.cpp:1538
UE4Editor_UnrealEd!UUnrealEdEngine::Tick() unrealedengine.cpp:366
UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:2355
UE4Editor!GuardedMain() launch.cpp:142
UE4Editor!GuardedMainWrapper() launchwindows.cpp:126
UE4Editor!WinMain() launchwindows.cpp:200
Head over to the existing Questions & Answers thread and let us know what's up.