Heatmap animation is flickering

This notebook https://plot.ly/python/heatmap-animation/ was posted almost two years ago. At that time the transition was smooth, like in this gif created from the animation generated in notebook.

heatmap_animation

Today I updated the notebook here https://plot.ly/~empet/14138 setting visible=False in axes definition, and increasing the frame duration, but the transition isn’t smoother and the animation is still flickering.
What was changed in the last ploty.js/plotly.py versions that led to this odd animation?