Recorder, by design, won’t produce fixed-rate movies. In particular, if there has been no change since the last frame, a duplicate frame won’t be added.
I’m not sure what you intend to illustrate with the clip you provide, but if it’s simply that the frame-rate doesn’t read 60, then that’s (probably) working as intended. If you can produce a movie which suffers visually as a result, then you have a problem.
If you see intermittent frame loss recording lossless RGB, you should check the destination drive can keep up. The free Blackmagic Disk Speed Test on the App store is handy for that.