Using the Round Coordinates filter yields no results.
How exactly did you apply it?
First, simply while editing the glyph in the edit view, I clicked “Round Coordinates”.
Then, I selected the nodes (all nodes) and clicked “Round Coordinates” again.
Both didn’t work.
You mean the command from the path menu? That works fine for me. What version of Glyphs do you have?
Yes, correct. I am on 3098. But I am also having issues with other things not working (Make Corner, for example, as well the HT Letterspacer). With Letterspacer, I found that it uses the robofab scripts, which are for Python 2, but those don’t work, as I have Python 3. Could this be related? Oddly, in Glyphs 2, everything works fine.
Can you send me that file?
Not right now, but I’ll ask Rainer 
The Letterspacer doesn’t work regardless of file, as it is some problem with my Python installations.
But the Round Coordinates is not using python.