Apologies for the video performance issue you're experiencing. The majority of the time these type of problems are related to a browser/network configuration on your end. There are currently no other open support cases or reports of video performance issues.
Our provider did experience a disruption related to the large scale DDOS last week but that was resolved on 10/21. At this point in time there are no known system issues that would diminish video playback.
I reviewed the Senior System Architect 7.1 course and saw no videos related to examination prep. Can you please provide me with specific details on what course and lessons you are trying to watch?
Some additional questions.....
Are other colleagues on the same network experiencing an issue with video playback?
Are you able to replicate the issue on different systems on the same network?
Are you able to replicate the issue in other browsers on the same system?
Are you able to replicate the issue on the same system but on a different network (eg. home or coffee shop)