First of all, I've seen this issue from at least 2024.1 to 2024.3 on macOS Ventura 13.6, but I'd suspect that it's probably been present on both OSes for quite a while due to the nature of it.
So, there's an odd, but very specific glitch I've run across a couple of times now. I've just figured out a fix, I think, but here's how to repeat.
1. In a precomp, set up a text layer and drag its source text to the comp's Essential Graphics.
2. Duplicate that text layer. Add a text animator. I'm using opacity to reveal my text.
3. Add any of the range controls from the text animator to the Essential Graphics panel.
4. Put that precomp into another comp and animate the range Essential Property.
5. Instead of animating smoothly, the text pops on from an arbitrary selection (i.e. not from the first character if you animate from 0-100%) and the selection glitches back and forth rapidly.
What seems to be happening is that, instead of treating the source text of that layer as its own thing (which should be the text you had set) it has some sort of error since you've duplicated a text layer with a linked Essential Property. I don't know if this manifests in other ways—I haven't seen it—but it otherwise appears to just have the same text as the original layer. If you duplicate the layer and change the Source Text Essential Property in the main comp, only the linked text changes, as would be expected. But for some reason, text animators get confused.
The fix is to do what I forgot to do before finishing my rig—link the Source Text of the duplicate to the Source Text of the first text layer (the one whose Source Text is in the Essential Graphics panel). Once you do that, the Source Text is explicit and it works smoothly.
Hopefully that makes sense.
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