When uploading a file, the dotted box with the words 'Attach' in the middle looks as if you can drag and drop your file into the area. See image below.

For this type of box, basic web usability states you can drag your file here that you want to upload. Doing so crashes CRM 2016.  If this is suppose to be a button, then please make it look like a button.  If you are supposed to be able to drag and drop, then it is not working.