[rtmpdump] why would rtmpsuck save small files while output full length data back to the browser

[Makc]

hello,

I was just trying to save recorded meeting from adobeconnect using the
tool from http://www.nirsoft.net/utils/rtmp_dump_helper.html along
with rtmpsuck windows build from
http://rtmpdump.mplayerhq.hu/download/rtmpdump-2.4-git-010913-windows.zip

The result was a bunch of screenshare_xx_xx files all 13 bytes in
total starting from "FLV |" (apparently flv header) but the actual
data was missing. At the same time the browser was playing them back
just fine.

Am I missing anything obvious about how rtmpsuck should work?