Hi respected Jerry 16,
Thanks for your valuable feedback and sharing updates with us and I really appreciate your effort and your precious time doing.
And I appreciate your kind words.
First of all, please accept my apologies. However, we appreciate your understanding, understand the inconvenience and apologize for it.
Based on my test for differences, it seems I can confirm that I also meet the same behavior when the document library or folder names contain spaces.
Since this issue only occur when the document library folder names contain spaces in SharePoint online Stream web part. I'm afraid it may need to check/investigate from the backend side via collect logs report.
As this Forum community has limited resources, the backend support team there has more permission than us, they have more resources to investigate the issue from the backend, they have Escalate channel to escalate your issue to check more and collect log reports for the root cause.
I would suggest you raise a support ticket from the Microsoft 365 admin center and report the issue to the related team. The more reports they receive from different customers, the more likely they will be able to find something affects users in common, do investigation and fix it soon.
Reference: Get support - Microsoft 365 admin | Microsoft Learn
Note: To create a support ticket, you need to have Microsoft 365 admin privileges and if you aren’t admin of your Office 365 organization, please contact the admin of creating a new ticket.
Reference: How do I find my Microsoft 365 admin? - Microsoft Support
Please accept my Apologies and I do feel regret for not resolving the problem and redirecting you to the related development team but the fix to your concern can be find out through the HAR logs and suggest you raise a support ticket from the Office 365 admin center, where the related team will investigate the problem further by collecting the HAR logs.
We are redirecting you to the proper one to solve the issue. That’s why we suggest you contact your admin or IT department. They can create support ticket. Once your admin or IT contact them, they will help you as soon as possible.
I'm sorry and I apologize for that.
Your understanding and patience will be highly appreciated. I hope that you are keeping safe and well!
Sincerely,
Waqas Muhammad