colormag not mobile friendly in GSC

I have been using colomag for several years for my association site, but I am using it on another site for a client. 

Since a few months, I realize that when I do the mobile friendly test or when I check the URLs of my sites on Google Search Console, every other time, I end up with mobile usability problems (unreadable text, because it's too small, and clickable elements too close together). 

And indeed, if you look at the visible rendering on GSC or mobile friendly, it's really not very pretty. 

Except that if I check on my cell phone, on any browser, in "private browsing", everything is consistent with what I expect from my sites (nothing to do with what Google sees ...). 

If I do these tests several times in a row, sometimes it is "green", and sometimes it is "red". 

I noticed something peculiar. When it's red, it's because Google is notifying errors in the "page resource" part. and this is what seems to be the problem:

- /wp-content/themes/colormag/dark.css?ver=2.0.7
- /wp-content/themes/colormag/fontawesome/css/font-awesome.min.css?ver=2.0.7
- /wp-content/themes/colormag/style.css?ver=2.0.7

I noticed that when I am in "Green" in mobile ergonomics, these 3 errors on these 3 css do not come up. 

Can you bring me your help and your expertise knowing that these symptoms are present on my 2 sites with your colormag theme. 

Thanks to you.

The page I need help with: [log in to see the link]