2.6.2 price problem with variable products

Hello, i have a price problem with variable products.

For a given variable product, the prices are defined correctly for every variation. When i visit the website logged in as admin the displayed prices are correct (for different variations) but when i visit the website as a visitor, all the prices for all variations are completely wrong.
My host is WPEgine and they confirmed that they disabled all the caching totaly:

here is the link: http://www.classpro.staging.wpengine.com

please help me with this, i think the problem appeared when i made the latest woocommerce update

Thank you in advance

### WordPress Environment ###

Home URL: http://classpro.staging.wpengine.com
Site URL: http://classpro.staging.wpengine.com
WC Version: 2.6.2
Log Directory Writable: ❌ Pour permettre les logs
rendez /nas/content/staging/classpro/wp-content/uploads/wc-logs/ accessible en écriture ou définissez un WC_LOG_DIR personnalisé.

WP Version: 4.5
WP Multisite: –
WP Memory Limit: 256 MB
WP Debug Mode: –
WP Cron: ✔
Language: fr_FR

### Server Environment ###

Server Info: Apache
PHP Version: ❌ 5.5.9-1ubuntu4.17 - Nous recommandons PHP version 5.6 minimum. Voir : Comment mettre à jour votre version de PHP ?
PHP Post Max Size: 100 MB
PHP Time Limit: 3600
PHP Max Input Vars: 1000
cURL Version: 7.35.0
OpenSSL/1.0.1f

SUHOSIN Installed: –
Max Upload Size: 50 MB
Default Timezone is UTC: ✔
fsockopen/cURL: ✔
SoapClient: ✔
DOMDocument: ✔
GZip: ✔
Multibyte String: ✔
Remote Post: ✔
Remote Get: ✔

### Database ###

WC Database Version: 2.6.2
:
woocommerce_sessions: ✔
woocommerce_api_keys: ✔
woocommerce_attribute_taxonomies: ✔
woocommerce_downloadable_product_permissions: ✔
woocommerce_order_items: ✔
woocommerce_order_itemmeta: ✔
woocommerce_tax_rates: ✔
woocommerce_tax_rate_locations: ✔
woocommerce_shipping_zones: ✔
woocommerce_shipping_zone_locations: ✔
woocommerce_shipping_zone_methods: ✔
woocommerce_payment_tokens: ✔
woocommerce_payment_tokenmeta: ✔

### Active Plugins (23) ###

Better Search Replace: par Delicious Brains – 1.2.10
BuddyPress: par La communauté BuddyPress – 2.6.1.1
Coming Soon Page & Maintenance Mode par SeedProd: par SeedProd – 5.0.3
WPBakery Visual Composer: par Michael M - WPBakery.com – 4.4.3
Loading Bar: par Alobaidi – 1.0.0
Loco Translate: par Tim Whitlock – 1.5.6
P3 (Plugin Performance Profiler): par GoDaddy.com – 1.5.3.9
Slider Revolution: par ThemePunch – 5.2.4
Stripe WooCommerce Addon: par Syed Nazrul Hassan – 1.0.7
Vibe Course Module: par Mr.Vibe – 2.1.2
Vibe Custom Types: par Mr.Vibe – 2.1.1
Vibe ShortCodes: par VibeThemes – 2.1.1
WooCommerce Extended Coupon Features: par Jos Koenis – 2.3.4
WooCommerce Checkout Field Editor Pro: par ThemeHiGH – 2.5.2
WooCommerce: par WooThemes – 2.6.2
WP Google Maps: par WP Google Maps – 6.3.13
WP Smush: par WPMU DEV – 2.3.1
WPLMS Assignments: par VibeThemes – 2.1.1
WPLMS Customizer Plugin: par VibeThemes – 1.0
WPLMS Dashboard: par VibeThemes – 2.1.1
WPLMS Front End: par VibeThemes – 2.1.1
WPLMS Demo3 Sample Data: par VibeThemes – 1.0
Woocommerce Social Reward: par XciD – 1.2.24

### Settings ###

Force SSL: –
Currency: EUR (€)
Currency Position: right
Thousand Separator: .
Decimal Separator: ,
Number of Decimals: 2

### API ###

API Enabled: ✔

### WC Pages ###

Base Boutique: ❌ Page non définie
Panier: #2078 - /cart/
Commande: #2080 - /checkout/
Mon Compte: #2159 - /my-account/

### Taxonomies ###

Product Types: external (external)
grouped (grouped)
simple (simple)
variable (variable)

### Theme ###

Name: WPLMS
Version: 2.1.1
Author URL: http://www.VibeThemes.com/
Child Theme: ❌ – Si vous modifiez WooCommerce sur un thème parent que vous n’avez pas construit personnellement
nous vous recommandons d’utiliser un thème enfant. Voir : Comment créer un thème enfant

WooCommerce Support: ✔

### Templates ###

Overrides: wplms/woocommerce/archive-product.php
wplms/woocommerce/cart/cart.php
wplms/woocommerce/content-product.php
wplms/woocommerce/content-single-product.php
wplms/woocommerce/emails/email-order-items.php
wplms/woocommerce/single-product/short-description.php
wplms/woocommerce/single-product/title.php
wplms/woocommerce/single-product.php

https://wordpress.org/plugins/woocommerce/