Underlining not working

Version: 6.1.4.2
Build ID: 9d0f32d1f0b509096fd65e0d4bec26ddd1938fd3
Mac OS Mojave.

The Underline function doesn’t underline! I’ve tried using the Toolbar button and also in the Font properties.
It just doesn’t underline!
Works perfectly OK in Calc and Impress but not in Writer.

is there a solution or should I file a bug?

Does the underlining work at least when you print the page, but doesn’t appear on the screen??

…or is it visible in the print preview mode?

… or does it work with different font?