Challenge with HTML5 file uploader with CMSB v3.14

As like everyone else I am thrilled that a solution to defunct flash image uploader has been found and integrated into CMSB.  I have a client that typically loads a LOT of photos at one time (sometimes 200) so I started testing the capacity of the new HTML5 uploader.  For these tests, I used both Firefox and Chrome,  there was some long hang-times when I would upload 7-10 at a time. Sometimes the browser would freeze or the screen would flash white and error but some of the photos were uploaded anyway, sometimes the browser would just freeze and I'd have to close the browser and reopen, sometimes CMSB would give the message "no files uploaded". Sometimes, like when I attempted to upload about 30 at a time the screen would freeze and show about 1/2 of them with "completed" and 1/2 with "100%" but the screen would just hang there and if I clicked "save" then the only images that actually saved were the ones tagged with "completed".  Any ideas?.