Glyph name textbox blocked?

What the title says. I click on the glyph name textbox and the text string gets selected, but the focus is on the code-points textbox and I cannot rename the glyph.

{D1F29D14-EF6F-40DA-B9C1-9CB4E761E86F}

We are not able to reproduce this behaviour. Is it specific to a font or a glyph?