If some requests from MapSVG to the server are failing without any obvious reason,
it could be caused by the
mod_sec Apache module that blocks suspicious requests.
What you could try to do first is disable
mod_sec entirely and see if that helps.
If it does, check the
mod_sec logs and find the reason of the blockage.
How to disable
mod_sec: add the following lines to the
.htaccess file in your WordPress root folder:
<IfModule mod_security.c> SecFilterEngine Off SecFilterScanPOST Off </IfModule>