Hi Rychu!
Were movie files in your folders 2013, 2016 and 2018?
What do you mean with Gui? The Nextcloud Sync Application or the Webinterface?
Your problem sounds quite like mine. Have a look:
I can’t help you right now, but you should edit your help request by following the “Example for a proper Nextcloud Support Post”. The informations you offer aren’t explicit enough.