A question about certain waveform

[NyaaX_X]

Hello everyone, long time~

Here I am wondering about a waveform-- I think I can meet them in the resonate inverter circuit. It seems like a sine-cosine wave combined together.
Like Steve ward's CCPS circuit here https://www.stevehv.4hv.org/transformer2/Simwave1.JPG.
And I fortuitous measured that in a tuning wireless power transfer circuit. But I don't know how to remake that situation... Can somebody share me how can that be generated?

PS. 4MHz ClassE SSTC is.. delayed, because I don't have time and proper instruments at home now days  :'(

Thank you everyone and Have a nice weekend~

[Aerogight]

Looks very simillar to a fundamental frequency overlayed with its third harmonic at ~1/2 amplitude. See attached picture.
I dont know what causes this waveform to appear.

[NyaaX_X]

That is similar.. but I think there're some differences like the dual peak are not continuously at the "switching" point.
And on Steve's site and others experience, those waveform was found as the Current waveform.
That "point" is at the bridge switching point for Steve's CCPS circuit https://www.stevehv.4hv.org/ccps1.htm.

By the way I get this waveform with voltage mode oscilloscope. Maybe that is not a proper connecting of the probe.. I just don't remember how I get them..