[Microsoft Store App Platform Flaws] UWP AdControl error: "unhandled ad exception: Script error"

An AdControl worked fine for a long time until it was revamped to cope with issues unrelated to the AdControl. This may well be coincidence. The AdCoontrol was generating the following error:
Type: Other
Message: unhandled ad exception: Script error.

Out of curiosity, I changed the AdContro to use the test version:

<UI:AdControl x:Name="ac" ApplicationId="3f83fe91-d6be-434d-a0ae-7351c5a997f1" AdUnitId="test"
Height="50" Width="320" ErrorOccurred="ac_ErrorOccurred"/>

It worked fine.  Then I changed it to use the ad unit of another app, it worked too.   I went to the ad unit page of the developer console, and found the ad unit had disappeared. I tried to create a ad unit, but the new one did not show up.  I tried to create another one with a name free of white space, it did not show up either.  However, the missing old unit suddenly showed up, and the AdControl started to function normally.

This is definitely an error of the server.