While images are uploading main thread is blocking

Hello, I try to upload images via Dropzone. I upload photos in groups of 3. My config is like below:

this.dropzone = new Dropzone("#dropzone-form", { url: window.DroNetConfig.api + "/multiImageUpload", paramName: "files", maxFilesize: 30, maxFiles: 3000, acceptedFiles: ".png,.jpg", autoProcessQueue: false, uploadMultiple: true, parallelUploads: 3, disablePreviews: true, addRemoveLinks: false, clickable: true, createImageThumbnails: false, resizeWidth: that.qualityWidthSize, } ...

But while sending every image group, UI is block and can't click anything. How can i resolve this problem? Is it a bug or am i do something wrong?