I have noticed this happen a few times and I am not sure exactly what is going on.
On the Start Computer Task module.
When selecting some computers normally a lot (20 or so) normally skipping some in the order of the list. Once I click on deploy selected it will pop up with a confirmation and once I confirm the tasks never process. When they do not process there isn't a confirmation message of it being successful.
I think this is amount that I am selecting but it could also be that they are not in order? I can do some testing or get you a log if you need it. Thanks!