How often does Sonar scan/record VST automation data?

Below is a relatively recent thread (2014) with links to some earlier ones.. I haven't re-visited this recently, but I think it's probably all still applicable:
 
http://forum.cakewalk.com/Automation-Write-records-inaccurately-m3040778.aspx
 
To summarize:
The minimum resolution that SONAR preserves automation nodes when thinning data written in real time seems to be on the order of 40ms, which is already twice the lowest rate (50Hz = 20ms), that you tested at, and seems to be consistent with your second screenshot. But there is also some logic around how fast the value is changing between ''samples', and when it's changing at rates that multiples of the automation 'thinning interval', you're going to get the kind of randomness and sync/phase error effects and variable time intervals that your screenshots show. Even understanding this, SONAR's thinning logic can be a little unpredictable
 
There is an AUD.INI parameter called AutomationDecimationMsec that is defaulted to 50 (ms), but according to comments by CTO Noel Borthwick in the older thread (2004) linked in the thread above, this setting is related to how data automation data are sent to plugins rather than how automation is thinned while writing it.
 
Ultimately, what SONAR records usually gives a reasonable facsimile of the original move when recording "real" moves made be hand from a control surface or with a mouse at the more gradual rates that automation is typically used. But when making extreme, oscillating moves to produce modulation effects, SONAR is not going to reproduce that well unless you draw the automation (or record CC data and convert it to automation envelopes in the case of MIDI).