Returning to wwise after a while so could be user error here, but some settings seemed to break during a project move to 2024:
In v2023 I recently created a very simple 24hr city ambience - a switch group switches between different district blends (park, commercial etc).
Switch Container
Blend Container A (Park)
Blend Container B (Commercial)
The switch container had fade-in and fade-out times of 4 seconds, which in 2023 worked as you'd expect - crossfading. After moving the project to 2024 the the fade-out from switching between B-A (B fading out) was not respected - it just cut abruptly, while other fades worked OK. After reseting all values to 0 and adding them again they worked as expected.
So nbd for me, but I think this might indicate that some properties can break on upgrade, could be risky at scale.