Issue loading fonts on Google Slides

[Pandorino]

It's about 2-3 weeks that I get this message in Google Slides.

I had some custom fonts setup and they can't be loaded, although they appear in the font selection list.

I've flagged this to Google but then I tested on Chrome and the issue does not appear there, nor on Firefox.

Also, in a Vivaldi private navigation window, the issue does not manifest.

The issue appears even if I disable all the plugins I've installed.

[Pandorino]

@Gwen-Dragon In Guest window, it works fine although I get this message

I can't make those presentations public since they're owned by the company I'm working for.

I tried to open Google Slides also in another window with another user and the issue does not appear.

The console log looks like this where I get the error: