Okay, here’s more info (and there are two related files I can send you separately as needed). The support staff just sent me the following:
I’ve taken a look at the output for the requests that go to /wp-admin/admin-ajax.php and it appears that there’s a difference in what we receive when the site’s working, compared to when it’s broken. I’ve attached a couple of text files with old (broken) and new (working) responses, with line breaks at each opening curled bracket.
If you put the two files in a diff tool, you’ll see that there are a handful of lines that differ, due to references such as “mapp0.getPoi(4).zoomIn()” being truncated to “.getPoi(4).zoomIn()”.
Let me know if this helps the developer track down where the issue may lie.