Component used: Fragment
Version used: 1.3.0-beta01
Devices/Android versions reproduced on: Google Pixel 4 XL

There are some key components here:

It only happens if you are using Fragments 1.3
It only happens if you are using androidx.transition 1.4 (not 1.2)
It only happens if you call startPostponedEnterTransition instantly after postponing

The effect is really noticeable when using the MDC transitions since they are currently not handling cancelations gracefully so it leaves the target view with alpha 0.

One fix is to always wait calling startPostponedEnterTransition at least one frame by posting to a handler or using yield() with Coroutines.

You may wonder why I'm calling start instantly and it's because the data is cached:

postponeEnterTransition(500, TimeUnit.MILLISECONDS)
viewLifecycleOwner.lifecycleScope.launch {
    // Imagine that loadData() does not suspend because the data is cached
    val data = loadData()
    setupViews(data)
    // Uncommenting this will mitigate the issue
    // yield()
    startPostponedEnterTransition()
}