Ashan,
The problem is in this error:
https://awardauction.net/wp_dev_site/eventontest/wp-admin/post.php?post=3622&action=edit
Uncaught TypeError: Cannot read property ‘1’ of null
at rgb2hex (eventon_backend_post.js?ver=2.8.9:201)
at get_default_set_color (eventon_backend_post.js?ver=2.8.9:155)
at HTMLDocument.<anonymous> (eventon_backend_post.js?ver=2.8.9:135)
at i (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils,underscore,backbone,wp-util,wp-backbone,media-models,moxiejs,plupload,wp-plupload,jquery-ui-cor&load[chunk_1]=e,jquery-ui-widget,jquery-ui-mouse,jquery-ui-sortable&ver=5.4.1:2)
at Object.fireWith [as resolveWith] (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils,underscore,backbone,wp-util,wp-backbone,media-models,moxiejs,plupload,wp-plupload,jquery-ui-cor&load[chunk_1]=e,jquery-ui-widget,jquery-ui-mouse,jquery-ui-sortable&ver=5.4.1:2)
at Function.ready (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils,underscore,backbone,wp-util,wp-backbone,media-models,moxiejs,plupload,wp-plupload,jquery-ui-cor&load[chunk_1]=e,jquery-ui-widget,jquery-ui-mouse,jquery-ui-sortable&ver=5.4.1:2)
at HTMLDocument.J (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils,underscore,backbone,wp-util,wp-backbone,media-models,moxiejs,plupload,wp-plupload,jquery-ui-cor&load[chunk_1]=e,jquery-ui-widget,jquery-ui-mouse,jquery-ui-sortable&ver=5.4.1:2)

No issues on dev2.