Bug - Opening projects that use 2020 drop-down menu expression controls (Pseudo dialog on startup)
I love the new drop down expression control effect in AE2020. Unfortunately though I have a bug on opening the project file. I get a dialog box similar to the attached screen grab for each instance I've used the drop-down menu as a master property. The code in the dialog changes for each instance.
For context, my project file features one precomp with a number of properties controlled by 3x dropdown menus on a control layer for colour, text option and positioning. That precomp is used in 5 other compositions, where using Master Properties I have used different drop down options for each. That means on opening the project file I get this dialog box 15 times (5x3 = 15).
It also doesn't save my previous combinations of master properties across the five comps, instead it will default back to whatever is the first option in the drop down – so I need to reset with every time I open the project, regardless of saving the project file.
Using AE 7.0.0 on macOS 10.14.4, MacBook Pro 15-inch 2018

This is fixed in After Effects 17.0.1, released last night. You may need to open the project, close it without saving, then reopen it and save to clear the errors. Please update and let us know if you’re still seeing any issues.
3 comments
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Alastair Mogford commented
Cheers John, that sounds good, I'll give your suggestion a try.
Many thanks
Alastair -
Hi Alastair,
Thank you for reporting this issue. We are aware of this bug and the team is taking a look.
The error has to do with the order of the compositions in the project structure. There is a workaround until a full fix is made: make sure that any pre-comps containing Dropdown Menu Controls which are used as Master Properties are at the top of the Project panel e.g. in a folder called "_Pre-Comps". The leading underscore will cause them to be sorted first alphanumerically and opened first when the project is opened. This should avoid the error and prevent the Master Properties from being reset to their default values.
Please let us know if this is helpful, or if you have any other questions.
Thanks so much,
- John, AE QE -
Alastair Mogford commented
One other thing - it appears that your choices for the drop downs via Master Properties aren't carried over when doing a render via Media Encoder (I assume because the AME duplicate file reopens forgetting the combinations), again just using default values