Fontawesome icons in DBC buttons not showing

I have a dash app in python that includes DBC buttons. The buttons in turn include an html icon component, which gets its content from the fontawesome library. These icons are showing correctly on most PCs, but there are exceptions on which the icons are not displayed. All PCs use an up-to-date version of chrome. What could be the problem here?

import dash_bootstrap_components as dbc
import dash

app = dash.Dash(__name__, external_stylesheets=[dbc.themes.BOOTSTRAP, dbc.icons.FONT_AWESOME])

app.layout = html.Div([
                dbc.Button(html.I(className='fas fa-pencil-ruler wc-drawing-icon'), 
                       id='open-drawing', class_name='wc-btn-open-drawing', color='primary'),
                html.B('Drawings', className='wc-component-title'),
            ], className='wc-component-container'),

I added wc-drawing-icon to the className of the icon to size it. The only thing it does is set font-size of the icon to 75px.