Compatibility issue with SharePoint Designer?

[Teresa Appelgate]

My group has set up a video channel in Stream, and I'm in the process of adding the videos to the group SharePoint Online site. Just linking the Stream webpart to the channel didn't produce the right results (couldn't configure the channel to display the videos the way the stakeholders wanted them--separate can of worms, to deal with later), so I ended up adding a separate webpart for each video and then arranging the webparts on the page. 

In order to arrange the webparts, I needed to tweak the webpart zone layout. I edited the zones in SharePoint Designer. When I refreshed the page in the browser, every Stream webpart was showing an error:

Cannot create an object of type 'System.Collections.Generic.List`1[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' from its string representation '(Collection)' for the 'Links' property. Correlation ID: 21a96c9e-9036-0000-7f34-49c2429ad758.

I went back into SD to see if I could spot an obvious issue. No luck, but saved anyway, then refreshed in the browser again. The Stream webparts now showed a different error:

One of the properties of the Web Part has an incorrect format. Microsoft SharePoint Foundation cannot deserialize the Web Part. Check the format of the properties and try again. Correlation ID: 97ab6c9e-70a1-0000-7f34-4994293f5a87.

 Does anyone know what's causing these errors, or how to fix them? The only solution I see right now is to delete and re-add the webparts (12 total).

[#2]

Hmmm, not sure where you are editing these webpart zones etc. assuming you are just editing the site page directly? You cannot edit the modern pages which contain the Stream web parts directly via SharePoint designer. Not even quiet sure even with SPFX you can either. Best thing you might be able to do is create custom full width web parts that contain the stream webpart/embed inside them.

[#3]

The site uses classic pages. 

[#4]

Didn't know there was a Stream web part for classic pages. doh! learn something new today.

[#5]

🙂 It might be wrong, but I think we are missing something here. Stream WebPart (the one provided by Microsoft) does not work on classic pages, it only works on modern ones...so not sure what WebPart is adding Teresa to the page

[#6]

It's there; when you add a webpart to a classic page, the Media and Content category has a webpart called "Stream(preview)" near the very end of the list of webparts. My first thought was that "preview" referred to the preview of the video that the webpart displayed, but maybe it actually refers to the webpart itself? In other words, it's not fully baked yet?

[#7]

Well, very strange I have just reviewed in both a classic and a modern site that when I add a WebPart to a classic page I don't have any of the modern WebParts provided by Microsoft so I don't know the reason why you are seeing this WebPart in a classic page