To be completed by the original poster:
CMS Version
Xibo Digital Signage Version 3.0.4
The CMS is installed on a VM with Docker Container.
In the network settings of the CMS the SSL options and STS are disabled, the SSL certificate is managed by HAProxy externally from the VM.
Player Type
Android.
Issue
The preview of a layout dont work if the layout contain a video. Once i try to use preview function, if i inspect the webpage i see the error: ERROR: Attempted to run Layout ID 148 before it was ready.
The preview of other layouts that not contain a video works well.
Please help