You're sending 85 characters and possibly more if you're got a CR or LF on the end. In the more recent versions of the IDE, that's enough to overflow the 64 byte read buffer. If you're early in your delay when the data is sent, some of it will get thrown away so your code will never see the 20th comma that triggers your serial prints of your results.
I'd suggest moving the printing code so that it runs every time you've received a character so you can see what you're getting. Or change the check to print when the currentCommand exceeds 10.
Once you satisfy yourself what's wrong though, you're going to want to ditch both the delays and the use of String; which sadly, looks like practically a complete rewrite. When you do, take a look at strtok - it's one way to parse out your data from a char array.