Wrong idx for click event on the scatter plotly chart

What I’m trying to do:
I want to build an app with clicking to change the color of the point.

What I’ve tried and what’s not working:
I tried to use click event in the chart, but when all points have the same x value, the click event return a wrong idx. When the x values are different, the returned idx is correct. Please check the project below.
Right chart works well, but the left one doesn’t work well. Is this a bug?

Code Sample:

# code snippet

Clone link:
https://anvil.works/build#clone:UJQO5RWI5IRIHHAO=6MY4JL7GZYJ5W2THU6C7FNRT

I only see one plot in your clone link?