there are 2 different errors in your e-mail:
1.) netLoadCalendar ... => unsuccessful "calendar-multiget" REPORT ... looks very interesting because we cannot do anything here - we simply say JavaScript/jQuery to perform the request and waiting for the result ... the interesting part is that jQuery executes the "error" callback, but then it returns 207 (2xx = success) ... you can try to experiment with jQuery (maybe jQuery bug) and report more details about this error (or create a temporary access to your server and send me a private message with credentials)