[BUG] Master Properties can't be changed with expression
I put this simple expression on a master property that cycles through some items. It shows 1, 2, 3, 1, 2, 3, etc. on the control, but it only shows the item #1.
timeToFrames(time/50) % 3 + 1;
This wasn't working on another master property, but it started to at some point on it's own. I've tried purging, recreating the property. About the only thing I haven't tried so far but sometimes works is recreating it all in a new comp.

This is fixed in After Effects 17.0.1, released last night. Please update and let us know if you’re still seeing any issues.
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Christophe Clarey commented
Hello,
I spent a lot of time today figuring out a problem with my expressions and I think it's related to that problem BUT it is still happening in AE 17.6.
I created a master property on the source text of a text layer in one of my precomp.
In my main comp, I placed an expression inside which returns the previous marker index.
The expression works if I put it on a basic text layer on the main comp. But once placed in the master property, it doesn't update and give all the time "1" as result (when the expression on the text layer return the expected number).If I don't put the complex expression but instead link the master property to the result of another text layer (with the expression), it still doesn't update (when the text layer does).
If, instead of complex expression, I place in the master property, the expression "time"... it works!! and it updates as expected.So, I may misunderstood something, but the problem seems not to had be completed fixed, at least for the Source Text.
I was initial working in CC 2019. Opened on CC 2020 (17.1.1) to see if the problem was solved but encountered the "time remap" problem. I had to upgrade to 17.1.2, time remap problem solved but not this problem. I decided to upgrade to 17.6 and... it's still there.
Do I miss something or is it still the same bug?
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Joe Clay commented
Colin, that was exactly what I was thinking until I found that solution. I didn't want to go back to 2019 either.
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Hi all,
Thank you for reporting this issue. The team is aware of this bug and will be working a fix.
I think it may have mentioned somewhere in the comments below, but a current workaround is to put a single keyframe or placeholder expression like "value;" on the original property. This should allow the keyframes and expressions on the Master Property to function as expected until a full fix has been made.
Thanks all,
- John from the After Effects Team -
Colin Harvie commented
I am also having this issue.
Joe Clay, thanks for mentioning that adding a key to the master property will allow the expression to work and pass the values to the pre-comp!Still a bug, but at least now I don't have to go back to 2019.
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Derek Rutkai commented
I am having this same issue but I only ran into it with AE 17.0.0 (AE 2020). I have 6 pre-comps with master properties. Only one of these pre-comp's master properties are animated and the rest are referencing that layer with expressions. like Joe said, the values are moving but the pre-comps are not being updated. Then I realized no expressions on master properties were working.
I have attached a file. All the blocks should be moving. It works for me in AE16.1.1 but doesn't work for me in 17.0.0.
Like Joe said, adding a key keeps the animation from being "frozen".
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Joe Clay commented
That’s a different issue. It occurred in older versions of AE. If you change around the properties you’ve added sometimes they’ll corrupt and one thing will control another and other things won’t work. The only fix I’ve found is to take everything into another comp and remind everything to the motion graphics panel. That has always worked.
That’s what I tried to say I attempted in this situation, but it didn’t work so that’s why is say it’s different. I think I’ve put in a report on that one too, but it’s under another user since we now have to log in with an adobe ID for some reason.
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Kira commented
I have a very similar issue, the master properties directly connected to other properties seem to work, others do not. Moreover I see the master property value is changing but it's not passed into the precomp.
At the same time, once I disable the expression and I start dragging the master property manually - everything works.
Is it the same for you?Adobe THIS IS A HUGE BUG! It breaks functionality of many projects
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Joe Clay commented
I figured out the difference between one that works, and one that doesn't. I must've accidentally added in a key. If the master property is keyed, the expression can change the master property. This is definitely a bug.
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Joe Clay commented
Recreating it doesn't work. Linking it to another slider works. However, if I add that expression to the slider, it still breaks in the same way. It's like it samples where it is at frame 0, and that's the only thing that works.
Didn't I see something in the notes about AE freezing expressions that don't change over time? It looks like maybe it's doing it here too because 2+1 does give me the third item. But as soon as it's something that changes, it doesn't work, like keying a linked slider. Changing the first key will change a linked master property, but the subsequent keys won't change it. Hopefully that make sense.