Just dug into the code and I think I’ve found the cause (thanks @Olov for investigating the 1000 point threshold - it helped to find the culprit). If you get a chance could you confirm it’s working for you too?
The issue here seems to be the renderer - see this line in the source code.
Switching the renderer to “svg” solves this issue for me.
px.scatter(df, x="time", y="value", render_mode="svg")
Also posted in the relevant plotly github issue.