(assuming you've selected 'Scheduled monuments' from the 'design my own topic' section and the orange dots are coming up to show you where the sites are)

sometimes it depends where you are, because not all the sites have stuff written for them. Then it'll come up with (eg) BA27 or SG76 rather than a long number with no letters. And then if you press to open the pdf it'll say 'no information available'.

otherwise, it's occasionally not cooperating at all and won't even bring up the map. But it seems fine for me this morning.