JavaScript errors

Got a series of errors/alerts like this one just now when opening this URL from DT 3.7.2 (on 11.6).

Not serious because I just cycled through until they stopped.

But might this be useful in future debugging; or is there even a way I can prevent them myself?

TIA!

Does this happen after viewing certain web archives, HTML pages or bookmarks? Then it might be an alert of the web page.

It was just this one site. First time. Opening a bookmark. I thought it was a site alert too, thanks.

But I wasn’t expecting it to be passed through to DT.