Bug Report Replay Buffer doesn't work.

[Brokoth]

I have been trying to use the replay buffer, with these recording settings:

• Recording Format: mkv
• Encoder: x264
• Rate Control: CRF
• CRF: 14
• Keyframe Interval: 0
• CPU Usage Preset: veryfast

However, it doesn't even save the clip in the first place. Before, i had used CBR as my Rate Control setting but with this the recording takes one minute plus to MAYBE record and even then, the recording is bugged.
How can i fix this?
My nvidia drivers and windows are completely up to date.