I have the exact same issue. I have a chooser that returns montages (as Asset Soft Reference)
The result is actually an array of real references and in 5.5 it they were resolved and it was working fine.
In 5.6 it doesn’t work anymore and I randomly get null refs to the montages.
I guess switching them to “Asset” instead of “Asset (Soft Reference)” would solve the issue, but I fear it would load all of them at once instead of lazy load them.
I’m interested in any fix or workaround this.
EDIT: I can confirm that turning them into “Asset” works but not sure it’s a viable solution if you have many of them.