The header of the real-time map seems to switch to an error message after a few seconds even though the map loads fine.
Interestingly I can't reproduce this issue on demo.matomo.org
There is no error in the JS console
Seems that the case when the ajax request, that is sent periodically to fetch new visitors, does not have any results
Okay, I found a bit more details. Indeed the initial request returns data, but the ones afterwards don't.
The first one sends
&minTimestamp=0 and the ones afterwards send
&minTimestamp=1610714405 and I guess if there were no new visits since the text is incorrectly updated.