Hi,
The pages concerned are WP built-in page post-type, but not all. They lead to the theme 404.php page. I didn’t let the plugin activated since I’m on a website in production.
I use a /%postname%/ permalink structure. The plugin list is :
Contact Form 7 by Takayuki Miyoshi – 4.7
Give – Extension de don by WordImpress – 1.8.6
GoogleGraph by Jordan Vrtanoski – 0.4.2.1
Leaky Paywall by zeen101 Development Team – 4.6.1
OneSignal Push Notifications by OneSignal – 1.14.1
Photographers galleries by Aurélien PIERRE – 0.4.2
PixProof by PixelGrade – 1.2.4
Table of Contents Plus by Michael Tran – 1601
Transposh Translation Filter by Team Transposh – 0.9.9.1
wBounce by Kevin Weber – 1.6.3
Woocommerce Gallery by Aurélien PIERRE – 0.1
WooCommerce PayPal Express Checkout Gateway by WooCommerce – 1.2.0
WooCommerce by Automattic – 3.0.2
WP eMember by Tips and Tricks HQ – v9.0.9
MailPoet Newsletters by MailPoet – 2.7.8
YITH Essential Kit for WooCommerce #1 by YIThemes – 1.4.4
YITH WooCommerce Bulk Product Editing Premium by YITHEMES – 1.2.1