Error uploading images in posts

I have some errors in my admin panel with uploading media in the posts section mainly like featured image cannot be added nor can i add any other media by uploading!

So i went to investigate what could be the problem there for i deactivated all my plugins and tried again and yes now it worked just fine so i started to activate my plugins one by one and checking each time and when i activated LayerSlider WP (wich is included in the theme package) the error reapeard again.

I noticed the LayerSlider WP that is included is an outdated version wich is version 5.1.1 the latest version is version 5.1.2 and 5.2.0b2 wich include many fixes so maybe its possible i can get the latest version since it is included in the theme package but there is no licence key given with purchase! Not using the LayerSlider WP is also not an option for me because the site then becomes a whole lot less attractive!!

I tried the LayerSlider WP with some of the default themes included in WordPress and they worked just fine so i have to come to the conclusion that there must be some error in the the theme somewhere or maybe in certain configurations or something i dont know. I really hope this can be resolved!

Kind regards Danny