Also I excluded the forum homepage from my cache plugin SG Optmizer but no success

Now the error in Inspect disapeared but still the text from the post won't show up to be edited

in case it helps this is the error I see in Inspect (Firefox)

one last information

I figured out the issue is related to my theme (a genesis child theme)

I switch to Twenty Twenty and editing the post worked

do you have any idea what I should do to fix it?

I managed to fix.
I had to manually update the theme.

You may close this topic.
Thanks