There was a change starting with version 21.09.20
Shotcut - New Version 21.09.20
You must have this version or a newer version of Shotcut.
There is no bug. Shotcut is working correctly.
In your video you have nothing underneath V3. If you had that clip on V1, it would work as you thought it should. With your last video just untick the checkbox, and opacity fade will work again.
With nothing on the bottom track.
With something on the bottom track.
