In Xinet versions 2019.2.1. and 2020.7 Portal DI is not passing the selected video aspect ratio to js player in Marquee which causes the video to be stretched. Keyframe thumbnails display in proper aspect ratio.
The defect causing the issue was addressed in Xinet version 2021.5. Please, upgrade Xinet Server and Portal to version 2021.5 or later using the steps provided in the Downloading Xinet Installers article.
After the update is complete, make sure the videos display in the proper aspect ratio.