Backoffice dashboard separates material icons with underscore

[arivei]

Hi,

I encoutered strange problem. I added some tabs in my backoffice menu, everything is working great, except for main (dashboard) backoffice page. Using simple material icons works, but icons with uderscore like menu_book get separated into menu and book, ie. rendering two icons instead of one. But only on the dashboard page! On product or any other page, it is displayed correctly.

I have tried to change the HTML code in my browser, copy it from other backoffice pages etc., but to no avail. I may pick different icon, but it seems like an interesting problem. I wonder if anyone tried to solve this?