I found that file chooser with this 1.6.0 official release version of the MidnightLib module gives the following character rendering error:

I remember I didn't have this error before when I added the FileChooser feature and sent you a PR #63:

From the interface it looks like the reset button is optimized, it should be after commit Improved layout and lists. In the next commit Show errors again and correctly handle closing you rename the functionButton to actionButton. So I think this one is incorrectly rendering the color block of colorButton.

This is just a side effect of the box being smaller. The character disappears when clicking into the field.

This is just a side effect of the box being smaller. The character disappears when clicking into the field.

I rechecked the code and it really doesn't seem to be a problem with the module code, it's supposed to be a bug in Mojang's writing of Minecraft.