Background:
When uploading attachments in the site entry requirements screen in the mobilisation and remobilisation workflow it is not very clear that you are able to drag and drop an attachment into this field (screen shot 1 no indication it is a drag and drop field).
Request for Change:
To be able to drag and drop the attachment you need to drop the attachment directly over the word drop (and this is only clear when you drag the document into the window and the word drop appears). If you do not drag and drop over the word drop then the attachment "misses" the field and then tries to open the document.
Look to make the ability to drag and drop more clear in this screen (refer to screen shot 2 for the reference on how small drop is to see and where the document needs to be "dropped").