FPS drops in recorded video, what's the problem?

Question

Video

I recorded the gameplay of the game in OBS, everything was fine. Two weeks have passed - I sat down to record again, but now when viewing the recorded, significant subsidence of FPS is noticeable, which was not there before. I tried to set a different bitrate, change the encoding method, the number of FPS when recording - nothing helped. PC configuration is great - 1080Ti and i7 8700k. What could be the problem?