Basically, it won't attach ... tried removing spaces in file name, tried image files rather than .pdf; tried editing the mark at the same time as adding a feedback file. It wasn't happy.
I tried Firefox - it attached immediately.
I'm using BB Q4 2014, Mac (Yosemite) & Chrome (the latest) - is this a known glitch, or is it just me. (Kind of hoping for the latter, as I have a number of staff who'd like to be able to do it!)