You are running into phase wrapping. In your particular case, 0 and 360 are essentially the same. What is probably happening is your phase is going slightly negative, but is being mapped into positive phase space. So instead of getting -0.01, you are getting 359.99. As a simple fix, if you know your phase should always be in the range -50 to 50 (for example), you can subtract 360 from values over 50 and add 360 to values under -50.
Phase unwrapping can get fairly complex, but should be fairly easy in your case.
As for your program, it is a fairly decent simple piece of code. You can remove the flat sequence (right click on the frame of the sequence and choose remove). It is doing nothing for you. LabVIEW dataflow already determines the sequence of those items contained within it.
If you need better performance, you can move your analysis to a different loop and use a producer/consumer architecture, but this is probably not necessary for the one-shot acquisition and analysis you are doing.
