Strange column width in treegrid

Hi, I’m having a problem with Vaadin 8 and Treegrid. I’m filling some columns with double values but some columns are too small for their content and some not. It does not depend on the lenght of the content.
Here is the code where I fill the columns:

for(int i = 1; i <= 13; i++) {
	final int ifinal = i;
	this.pLAGrid.addColumn(user -> user.getSingleValue(Integer.toString(ifinal)), 
		//show exactly two digits after the comma
		new NumberRenderer(new DecimalFormat("0.00"))).setCaption(Integer.toString(ifinal)); 
}

I have added an attachment with a screenshot of the resulting grid. As you can see it doesn’t depend on the numbers length if the column is wide enough or not. I didn’t change the expand ratio or the width of the columns anywhere.
We use Open Sans so I thought, maybe it has to do with this issue: https://github.com/vaadin/framework/issues/8502
Does anyone have the same problem or know what to do?

17433653.png

I noticed now that it doesn’t happen in Chrome, only in Firefox and Edge.