This is funny. I've been trying out the Cascadia Code font without issues. Yesterday I upgraded to the new font release (1911.20) and now it looks like this in PhpStorm (even the font name itself is corrupted!):
It's funny because only the main font looks weird (the three other fonts from the same family are correct) and it only happens in PhpStorm (LibreOffice Writer or Visual Studio Code render it just fine).