Uploads no longer work in internet explorer, wordpress 5.1.1

Hi,

When attempting to upload an image in internet explorer the file dialogue box opens, I select an image but then it does not upload.

Using the console debugger to inspect the error it fails in buddypress-activity-plus/js/external/fileuploader.js line 1148

add: function(file){
	if(!(file instanceof File)) {
		throw new Error('Passed obj in not a File (in qq.UploadHandlerXhr)');
	}

	return this._files.push(file) -1;
}

This is specific to internet explorer, chrome still works and uploads the images fine.

I have a duplicate install running WordPress 4.9.8 and it works fine so I’m assuming something in the upgrade to WordPress 5.1.1 has stopped this plugin working.

There are extra security checks noted here:

Backwards Compatibility Breaks in 5.0.1

Could it be to do with that?