QT Signals are lost after some time

Using C++, Qt 4.8, Google Protobuf 2.4.1 I have a plugin that sends several commands over a port, and these commands are then interpreted in another plugin, which emits the commands as Signals. Upon the reception of each signal a slot is called, which executes a specific task. Each task takes around 1-2 second, to be completed, after which the plugin waits for the second signal in the queue, and runs all over again.

The problem is, if I send quite a few commands eg: 500, not all of them get received (even though they are the same command). The amount of commands that are received is completely random, even if I send the exact same commands, with the exact same parameters.

My question is, is there some sort of a limit as to how many Signals can be queued up? Or is there any time period after which the Signal expires? Or anything that I might be missing?

I am lost and haven't spent too much time using QT... p.s. the plugin does not crash, or do anything fishy.. it just does not receive any more signals.