Getting 405 - Method Not Allowed on some requests while uploading images via BlueImp FileUpload

I am getting 405 - Method not allowed error for some requests when I try to upload images from BlueImp FileUpload plugin. This normally happens when I try to upload more than 6-7 images. These are the requests. Each request represent a separate file upload request

This is the request headers, request and response of one of the failed request

via Chebli Mohamed