Hi,
just for completing my problem : I tried to migrate on Moodle 3.5., but the problem is still here. I must have something on my server configuration to explain it all, that must be the only answer !
However, I found a little solution just by adding one line in comment. Now, after connect, user goes directly to the acceptance page, without having to read all the different pages of my policy. Of course, on the acceptance page, he still can read them, for each policy shows a link to (re)read it before accept.
I went in moodle > admin > tool > policy > classes > output, opened the file pageagreedocs.php, and commented line 308 which calls redirect_to_policies :
307 // Redirect to policy docs before the consent page.
308 //$this->redirect_to_policies($userid, $myurl);
I still can't bring a better explanation, for the problem occures only on my prod instance (but not on my test platform !!). I should do deeper testings, but when...
Olivier