IF the dcc send command is given manually, the bug does not occur and sends are sent at the highest possible speed
I think this maybe where the problem is, if its not a manual command it is a automated command so is seen as a fileserver.
If u need a work around try one of these (i dont know if they work)...
.timer 1 0 dcc send nick filename
or if that doesntwork try...
.timer 1 0 .timer 1 0 editbox -s $!editbox(Status Window,0) $chr(124) editbox -sn //dcc send nick filename