Actually , If you don’t make some kind of fix/addon, LMS team asked (if possible) for your team to provide info on conflict and they will check it themselves. Here is direct quote:
“Our theme “DesignThemes Core Features Plugin” does not have any conflict with the Featured image. Can you please check with the “FV Player” plugin support team and let us know if we need to change anything from our side for the featured images to work, so that we can check and let you know.”
I know this thread is old but I have same issue. Same website Haris was doing. Both FV player and LMS responsive theme from wedesignthemes (https://goo.gl/RJ8hdO) are updated to latest versions at the moment.
Conflict comes when both “DesignThemes Core Features Plugin” and this player are activated.
I could provide code or files from said plugin. Maybe its something minor,…quick fix for you guys?