Unable to Attach File Due to "Missing Token"

I was trying to attach some files to MCL-16913 seeing as it was fixed and that there were more details on WEB-3366 that I was attaching, however whenever I tried it, it said that it has not uploaded and there was a "missing token", and it told me to try attaching the file again. Yet every time I tried it, the same message appeared, over and over...