On Fri, 2017-06-16 at 11:17 +0200, Eric Détrez wrote:

Hello

Just a message to explain a problem I had and the answer.

The trouble : the big parenthesis were not big, $($ and $\bigl($ gave  the same shape

The fix : I defined my own environment in which I defined very big font sizes. \definefontsize[e] \definebodyfontenvironment  [default] [e=4]

One of them was \definefontsize[g]

I changed it to \definefontsize[gg] and all went right again

Cool.  Now try $\biggl($

The explanation (?) : maybe \big was read \bi (bold italic) with size g  ????

I had this problem for 2 years, I'm happy to have figured it now.