Am a keen follower of Microsoft's SharePoint Blog and proud to provide this direct from the Microsoft Tech Community:

On March 24^th we shared in an announcement in the M365 message center (MC207439) details around temporary adjustments we are making to select capabilities in SharePoint Online and OneDrive.

During these unprecedented times, we are taking steps to ensure that SharePoint Online and OneDrive services remain available and reliable for your users who depend on the service more than ever in remote work scenarios. 

Note: These temporary feature adjustments may be in place during business hours in your tenant's region.  

Content migration, Data Loss Prevention (DLP), and backup solutions 

Many SharePoint Online and OneDrive customers run business-critical applications against the service that run in the background. These include content migration, Data Loss Prevention (DLP), apps that scan the service and backup solutions.  In support of the objective to remain highly available, we are moving some operations to regional evening and weekend hours.

Users may observe: 

• Migration, DLP and backup solutions may achieve limited throughput during regional weekday daytime hours. During evening and weekend hours for the region, the service will be ready to process a significantly higher volume of requests from background apps. 

Please review the relevant best practice guidance, which describes how to get maximize throughput. 

• Migration performance guidance , which includes an FAQ & Troubleshooting section  
• For DLP, Apps that scan the service & Backup apps: Best practices for discovering files and detecting changes at scale  

File Management 

Various background processes to manage new media (images, videos) may now be processed during evening and weekend hours.  

Modified processes include: 

• Users may experience reduced video resolution for playback videos. 

• Customers who use OneDrive Files On-Demand and choose to “display items by using large thumbnails” in Windows Explorer or Mac Finder will see generic icons instead of thumbnails.

  Note: Photo file thumbnails (jpeg, jpg, png, etc) are not affected by this change.

  The affected thumbnail types are categorized as the following:

  • Video and PDF files: pdf, avi, mp4, mov, mpg, etc.
  • Document files with generators: docx, txt, html, etc.
  • New extensions likely to be permanently blocked because no thumbnail generator is ever likely to exist:  reg|bak|iso|nupkg, etc.
  • Files types already blocked today because no generator exists: lnk|xlsx|xls|url|exe|zip|rar|rdp|apprefms|msi|website

  There is no workaround, we will continue listening to feedback and iterate on this approach.  

Additional Information  

• Temporary changes in process schedule for SharePoint Online services
• Our commitment to customers and Microsoft cloud services continuity 
• Awareness of temporary adjustments in Microsoft OneNote

We will provide further updates to this post as the situation may change.

Last article update: 07/1/20

The above is kindly provided by the Microsoft Tech Community!