Thanks for getting in touch - and thank you for your recent PingPlotter Pro purchase! We appreciate it.
It's tough to say for certain why your MOS score seems to be sticking at 4.37 without a bit more information. If possible, would you be able to send us over a screenshot of what you're seeing, as well as a .pp2 file of your trace results (via the "File" -> "Export Sample Set" option in program)? You can post that info here, or send it to us via email at email@example.com - and we'll be happy to take a look from there!