Mobile layout not resolving correctly

We use WPmovieLibrary plugin and on the above page the numeric and Alpha index header (grid) does not resolve in mobile view. It resolves successfully in our original theme but it just set a long tall column of numbers in mobile view on large smart phones (Samsung Note4). please take a look at the above URL via a mobile to see the result.

Resolves ok on desktop, tablets and iPad but not in mobile layout. I think it better to look at the site page instead of posting screen shots.

Is there something I am not setting in customiser or if not then this is bug in the hueman pro theme?

currently our site has a 35% mobile hit rate so this is important to us.

# SITE_URL: https://www.lasouterraineenglishlibrary.fr
# HOME_URL: https://www.lasouterraineenglishlibrary.fr
# IS MULTISITE : No

# THEME | VERSION : Hueman Pro | v1.0.28
# WP VERSION : 4.9.4
# PERMALINK STRUCTURE : /%postname%/
# 30 ACTIVE PLUGINS :
– Admin Branding (version 1.1.2)
– Advanced Access Manager (version 5.0.8)
– AWSM Team (version 1.1.2)
– Carousel Horizontal Posts Content Slider (version 3.2.6)
– Cookie Law Info (version 1.5.3)
– Currency Converter Widget (version 1.0.1)
– Disable XML-RPC (version 1.0.1)
– Email Subscribers & Newsletters (version 3.4.8)
– Email Subscribers – Group Selector (version 1.4.2)
– Formidable Forms (version 3.0.05)
– Gmedia Gallery (version 1.11.4)
– GTranslate (version 2.8.36)
– Heartbeat Control (version 1.2.3)
– Imsanity (version 2.3.10)
– List category posts (version 0.75.2)
– Postie (version 1.9.16)
– Random Text (version 0.3.0)
– Regenerate Thumbnails (version 3.0.2)
– SG Optimizer (version 4.0.0)
– Simple Calendar (version 3.1.14)
– TinyMCE Advanced (version 4.6.7)
– WordPress Book List (version 5.5.3)
– WordPress Database Backup (version 2.3.3)
– WP-Optimize (version 2.2.0)
– WPBookList Bulk Upload Extension (version 1.1.1)
– WPBookList Carousel Extension (version 1.0.0)
– WPBookList Kindle Preview Extension (version 1.0.1)
– WPBookList Mobile Extension (version 1)
– WP Google Maps (version 6.4.09)
– WPMovieLibrary (version 2.1.4.7)

# PHP Version: 7.0.27
# MySQL Version: 5.6.36-82.1-log
# Web Server Info: Apache

# WordPress Memory Limit: 768MB
# PHP Memory Limit: 768M
# PHP Upload Max Size: 128M
# PHP Post Max Size: 128M
# PHP Upload Max Filesize:128M
# PHP Time Limit: 120
# PHP Max Input Vars: 1000
# PHP Arg Separator: &
# PHP Allow URL File Open:Yes
# WP_DEBUG: Disabled

# Show On Front: page
# Page On Front: Welcome(#5)
# Page For Posts: (#0)

The page I need help with: [log in to see the link]