The reason there seems to be a difference in quality/resolution is that the two videos being played are adjusting to network conditions. The more available bandwidth, the higher quality/resolution you will see. The videos are delivered using adaptive bitrate streaming.

Solutions:

First, try to refresh the browser window. Refreshing may renegotiate available bandwidth and (if available) force the higher quality video to be streamed. 

If refreshing does not work, and you are confident it is not a network limitation, you can force the videos to play at the highest quality by appending the URL with "?usehtml5=true" (without the quotation marks) on any presentation.

For example, if the URL of the presentation is

https://vid.umd.edu/detsmediasite/Play/e9bd1898852e41f5934200405b19efc31d

and you append the URL to read

https://vid.umd.edu/detsmediasite/Play/e9bd1898852e41f5934200405b19efc31d?usehtml5=true

the videos will be forced to stream the highest quality/resolution to your browser.

Note: If you begin to experience excessive buffering after attempting this workaround, it is likely there is a constriction in bandwidth somewhere between you and the campus servers and you should revert to the original link to view the lecture videos. 

If neither of these options work for you, please email dets-support@umd.edu for assistance.