The expressions themselves check out. When I adjust the value of the Slider scale the layers' opacities adjust accordingly. However as soon as I try to keyframe the slider values, the expression freezes to whatever the first keyframe value is. So basically if "Layer B" is visible when I start key-framing, only "Layer B". will be visible from that point forward, no matter the change in Slider value.
I hope I've explained this thoroughly enough. I'm very confused as to why the keyframes would be the issue. I thought initially that I might have too many compositions and too many expressions, however I stumbled across a thread where someone said they have "600 comps and 8000 expressions" and everything works fine.
Is there some setting that I'm missing here? It's only been a problem within this composition.
Any help would be much appreciated. Thanks in advance!
This will happen when you're referencing a keyframed in (or from) a precomp and the precomp doesn't start at time zero in the main comp. You have to compensate for that offset in your expression by using valueAtTime() with an offset equal to the start time of the precomp layer in the main comp. The exact code depends on how you have things set up.