Khan Academy version 7.0.2 (34973)
iOS 13.7
iPhone X

The completed lesson indicator (blue circle and a white check mark) is not added to lesson until the video page is closed and reopened.

On a video page, in this case:
Arithmetic > Unit: Multiplication and division > Multiplying by 10s

https://imgur.com/a/liowFhQ

(details for why the screenshots were uploaded to imgur, at the bottom of this post)

Scrolling down to the “Up next” section.

After opening and completing the lesson with the same name: Multiplying 10s

Then the video page opens again, but the just completed lesson did not get the completed lesson indicator.

https://imgur.com/a/CUUiRh7

Clicking on the back button in the top left corner of the video page opens the previous page: Unit: Multiplication and division

There the Multiplying 10s lesson is shown with the two purple rectangles: 80/100 points.

https://imgur.com/a/3jw3VY0

Opening the video page again: Multiplying by 10s

Pausing the video (not needed but one probably don’t want to let it play while scrolling down)

Scrolling down to the "Multiplying 10s" lesson, shows that it now has the completed indicator.

https://imgur.com/a/jTtcBC4

Notes:

The completed lesson indicator is added when a video has been watched, without having to reopen the video page.

https://imgur.com/a/yqKoiNO

But the indicator is not added to the lessons, even when completing two lessons in a row on the same video page.

https://imgur.com/a/2SrcahS

The screenshot above once again shows that the indicator is added to the next video after its been played.

Expected:
The completed lesson indicator should probably be added right after completing a lesson without having to close and reopen the video page.

Imgur:

The screenshots were uploaded to imgur, because when an attempt was made to add an image to this Details text box:
- By pressing the Insert image button
- or by dragging an image from the Windows File Explorer and dropping it on this Details text box

Then this error message at the bottom of the Details text box appeared:
You can only upload images (jpeg, gif or png). Image uploads are limited to 2 MB.

The largest of the 6 images is 23.4 KB.

The forum guidelines:
https://support.khanacademy.org/hc/en-us/articles/115006770788-What-are-the-guidelines-for-posting-links-images-and-videos-on-the-community-forums-

state that:
Please try to limit your image size to <600 px width and height.

It didn't help to resize the height (the larger of the width and height dimensions) to 600px, but the same error message appeared, and 500px showed the same error message.

I've been able to include iPhone X screenshots after resizing their height to 600px in previous posts (a day or two ago), so I'm not sure why it isn't working today.