Steps to reproduce the issue

1. Go to administration side
2. Go to Système > Configuration > Tab Serveur > Paramètres du serveur
3. Change value in the field Rapport d'erreurs: from old value "Aucun" to new value : "Maximum"
4. Click Save button, page is saved and reloaded
5. but you see the old value "Aucun" in the field Rapport d'erreurs
6. Refresh (reload) the page in the browser by clicking Reload the current page button in the browser's menu
7. Now you will see the new value: "Maximum" in the field

Expected result

After clicking Save button new saved value must be displayed without any additional action

Actual result

You have to reload the page in the browser in order to see new saved value (or click two times on the Save button)

System information (as much as possible)

PHP exécuté sur Linux 2018 x86_64
Type de la base de données mysql
Version de la base de données 5.5.30
Interclassement de la base de données utf8_general_ci
Collation de la connexion à la base de données utf8mb4_general_ci
Version de PHP 5.6.39
Serveur web Apache
Serveur web pour interface PHP fpm-fcgi
Version de Joomla Joomla! 3.9.4 Stable [ Amani ] 12-March-2019 15:00 GMT
Version de la plateforme Joomla! Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT

Additional comments

I've tested the issue on my Windows 7 64-bits
my browser: Chrome Version 73.0.3683.86 (Build officiel) (64 bits)

Cordialement.