Formatting options not working in upfront

Hi there,
I am using the Spirit them with Upfront to build my website.
I am encountering a roadblock in the formatting of the test boxes on my pages.
Indeed at first I was able to chose a Heading/paragraph style for the text and then to change the formatting of some words directly in the upfront interface, for example, making one word "bold" or changing the color. This is not working anymore. I am still highlighting the word, choosing "B" for bold as formatting from the pop-up formatting bar but the text formatting is not changing.
I am not sure but I believe this started following the last Upfront update.
Do you have a fix for this?
Thanks & regards