This solution works perfectly when using an Arduino Mega with LabVIEW 2019. Before I implemented this fix and uploaded it to the Arduino I would receive error 5003 on the Uno and error 5002 on the Mega. After implementing the checksum fix I was able to get thing working on both devices. Thanks for posting this fix. It was a lifesaver!
Initialize the checksum variable to ZERO work perfectly. No need to use and old Arduino version.
Thanks Thomas Plummer!!!