Hi Pierre,
I’ve spent more time on this today and went through the live site and disabled almost all of plugins.
As soon as I activate AMP i get this error in the consol and cannot create a new gallery. Turn off AMP and the error message goes away and the create Gallery button re-appears.
Thank you
JQMIGRATE: Migrate is installed, version 1.4.1
load-scripts.php?c=1&load[chunk_0]=hoverIntent,common,admin-bar,suggest,wp-ajax-response,jquery-color,wp-lists,jquery-ui-mouse,jquery-ui-sortable,postbox,jquery-ui&load[chunk_1]=-position,jquery-ui-menu,wp-dom-ready,wp-a11y,jquery-ui-autocomplete,tags-suggest,tags-box,word-count,wp-sanitize,post,editor-ex&load[chunk_2]=pand,thickbox,shortcode,backbone,wp-util,wp-backbone,media-models,wp-plupload&ver=5.3:414 Uncaught TypeError: Cannot convert undefined or null to object
at g.cleanup (load-scripts.php?c=1&load[chunk_0]=hoverIntent,common,admin-bar,suggest,wp-ajax-response,jquery-color,wp-lists,jquery-ui-mouse,jquery-ui-sortable,postbox,jquery-ui&load[chunk_1]=-position,jquery-ui-menu,wp-dom-ready,wp-a11y,jquery-ui-autocomplete,tags-suggest,tags-box,word-count,wp-sanitize,post,editor-ex&load[chunk_2]=pand,thickbox,shortcode,backbone,wp-util,wp-backbone,media-models,wp-plupload&ver=5.3:414)
at g.off (load-scripts.php?c=1&load[chunk_0]=hoverIntent,common,admin-bar,suggest,wp-ajax-response,jquery-color,wp-lists,jquery-ui-mouse,jquery-ui-sortable,postbox,jquery-ui&load[chunk_1]=-position,jquery-ui-menu,wp-dom-ready,wp-a11y,jquery-ui-autocomplete,tags-suggest,tags-box,word-count,wp-sanitize,post,editor-ex&load[chunk_2]=pand,thickbox,shortcode,backbone,wp-util,wp-backbone,media-models,wp-plupload&ver=5.3:414)
at r (load-scripts.php?c=1&load[chunk_0]=hoverIntent,common,admin-bar,suggest,wp-ajax-response,jquery-color,wp-lists,jquery-ui-mouse,jquery-ui-sortable,postbox,jquery-ui&load[chunk_1]=-position,jquery-ui-menu,wp-dom-ready,wp-a11y,jquery-ui-autocomplete,tags-suggest,tags-box,word-count,wp-sanitize,post,editor-ex&load[chunk_2]=pand,thickbox,shortcode,backbone,wp-util,wp-backbone,media-models,wp-plupload&ver=5.3:414)
at l (load-scripts.php?c=1&load[chunk_0]=hoverIntent,common,admin-bar,suggest,wp-ajax-response,jquery-color,wp-lists,jquery-ui-mouse,jquery-ui-sortable,postbox,jquery-ui&load[chunk_1]=-position,jquery-ui-menu,wp-dom-ready,wp-a11y,jquery-ui-autocomplete,tags-suggest,tags-box,word-count,wp-sanitize,post,editor-ex&load[chunk_2]=pand,thickbox,shortcode,backbone,wp-util,wp-backbone,media-models,wp-plupload&ver=5.3:414)
at h.Collection.n.off (load-scripts.php?c=1&load[chunk_0]=hoverIntent,common,admin-bar,suggest,wp-ajax-response,jquery-color,wp-lists,jquery-ui-mouse,jquery-ui-sortable,postbox,jquery-ui&load[chunk_1]=-position,jquery-ui-menu,wp-dom-ready,wp-a11y,jquery-ui-autocomplete,tags-suggest,tags-box,word-count,wp-sanitize,post,editor-ex&load[chunk_2]=pand,thickbox,shortcode,backbone,wp-util,wp-backbone,media-models,wp-plupload&ver=5.3:414)
at i.c.<computed> [as off] (media-views.min.js:1)
at i.dispose (media-views.min.js:1)
at i.dispose (media-views.min.js:3)
at i.remove (media-views.min.js:1)
at underscore.min.js:1