If you have 519 clips, then the length of the total response is very big. The standard frame size of an Ethernet packet is 1500 bytes. I assume that V-Control thinks the Acknowledge is complete before the whole Acknowledge is received.
To solve this you need something such as a termination character or sequence. I can imagine that chr(13) is not suitable because it might be multiple times in the Acknowledge.
You need to find a single character or a sequence of characters that marks the end of the transmission and define that as TermChar.
At Configure->Options in the System Tab, there is also a “Maximum Channel Buffer Size” value, set to 600 by default. If the length of the Acknowledge exceeds this size, then the Acknowledge will be dropped. So you might need to increase this value.