In your original pictures, you applied a filter to the whole track, but in your second post you don’t have track filters applied. What filter did you apply to the whole track?
opacity fade on v2.mlt (8.7 KB)
It works for me on 18.07 just fine.
Yea the audio preview is sketchy. It does not affect the final result. Not enough for me to convert back to a previous version.
For others who may be reading, the audio preview has been discussed here: Sound Bug after v18.07 Update