I’ve checked my project today and i get the same issue.
I am yet to find a solution but i think i have pinned down a root cause.
In the base we wanted the label to always face the camera in case we ever rotate the base and to do this we had to use a label3d node and not the UI version of the label.
In doing this the settings are different and there are a few options that affect this. The Pixel size, The Font size and the outline size.
Now i havent managed to work out settings that improve this but the tooltip says to increase the font size whilst decreating the pixel size at the same time.
As said i havent worked out settings that work but this is the reason that we get the issue because in the label 2D we are using a 64 size for font and in the label 3D for the base we are using 500. Quite a bit of a difference.
Hopefully playing with these values will yield a better result but so far i am not having much luck improving it especially with the outline forcing itself to a size dependant on the font size (IE 1000 font size forces the outline to 127 for some reason)
Hope this at least gives you a thread to pull on.
Edit :- I added a seperate Label2D to the main scene to show the difference between the 2D and 3D nodes