Hi
I can not help you with the signs, but I have two possible solutions to stop to revert to Arial.
Radical solution (recommended): delet Arial. If you have access to Frutiger, you will never, never, never again want to use Arial. This, and most other M$-Fonts are completely banned on my computers. They are just not necessary.
Scribus solution: follow the screenshot in the menue -->Files. Do that first thing for every new project, this will stop the mess with the hundreds of availabel fonts on your computer. Just add another one, if you need a new font while working.