Spinning ball with Font change in Mac OS High Sierra and Scrivener 3.0

With a project that uses a defined style, an attempt to change the font for a specific line of text by using the drop down window to the right of styles results in the spinning ball. However, changing the font by clicking on Format—Font works OK, meaning, no spinning ball?

Could you please send us the project for testing?
Thanks and all the best,
Keith