Thank you for your answers.

The problem occurs punctually and therefore the parameter setting is not in question.
But I understood the cause.

I use BIAB in a configuration with 2 screens. But the WE I have a configuration with a single screen. And when I open BIAB it often happens that BIAB does not appear, as if it opens on the second screen.

To circumvent this pb I erase the file preference/intrface.bbw.
The link between this deletion and the pb mentioned is now proven!

If there is a trick to make BIAB appear without deleting the intrface.bbw file, I'm interested.

Best regards