I'm not sure why, but when you drop a folder, the max number of files queued is 99.
It works fine if you navigate into the folder, select all files, and drag and drop the selection.
I'm assuming this is a browser limitation. Can you see if you get an error in the console and please provide information about your browser.
sorry just now saw the reply.
Chrome Version 45.0.2454.101 (64-bit)
No console errors or messages.
Found this issue, which I think is the same: #1037
Fix problem with more files than 100 in a directory
#1037 #599 #1070 Closes #956