Odd Low Setting Behavior With Helix Syn V

I don't think this is normal function, but wanted to see if anyone else has encountered it.  When I have the low setting on for any pattern that pulses, the vibration occasionally slips into what I'd almost describe as a "whisper mode," where the vibration is extremely subtle, and then jumps back into the typical low setting power.  It's random, sometimes happening after the pulse pattern is done, sometimes in the middle of the pattern. This only happens on the low pulse settings.

I can't figure it out: I don't necessarily mind it, but I'm also not sure if it's an indication of a malfunction.  Still well within the warranty period.  Anyone else experience this?