There's also a VISA Open in the Configure Serial Port VI. If you believe the "old" serial VIs work any differently, they don't. They use VISA. They only exist for backward compatibility, so that old code that used them would still load in newer version of LabVIEW. NI changed those VIs a long time ago to use VISA.
I haven't looked at your code, but what Dennis said seems to be the real cause of your issue. If the messages you get terminate with a character such as a linefeed, then you should not be used Bytes at Serial Port. You configure the serial port to use termination characters, and set the termination character to what it's supposed to be. Then you simply feed a large enough value for the byte count to VISA Read. VISA Read will automatically stop reading once it sees the termination character. Please read the documentation on these functions.
