TextmeshPro Rendering problem when on 21:9

I have some Text using TMPro on a World Space canvas, and when I put the aspect ratio to 21:9 the characters render with a transparent background ( see images attached)

The same thing doesn’t happen at 16:9 16:10 or 4:3.

Does anyone have a clue why, or how I can fix this ?

These visual artifacts are related to the Ratio of Sampling Point Size to Padding being too small. See the following post .