Uploading thousands of objects to s3 signed URL

We are currently running into an issue when uploading thousands of images with the aws-s3-multipart plugin. Upon commencement of upload, the UI displays ‘preparing upload’ whilst it attempts to sign all the URLs at once. This usually causes a huge slowdown, often crashing chrome. It seems that the limit function only affects concurrent uploads and not the signing side of the process. Is there a known solution to this?