Having problems with background noise reduction in final cut pro x

I often cut up a video into multiple clips and paste them together in the timeline. I am trying to remove fan noise, AC noise, etc. Final cut actually does a good job of this when it works. But for each clip in the timeline, the effect fades in as the video is playing. So basically, at the beginning of each clip, you hear the fan and in a few seconds it fades out and the audio is exactly what I want...until the end of that clip. When the timeline reaches the next clip (same original video shot, just a different segment), the fan noise returns and fades out again after a few seconds.

I have tried the following to no avail. Of course, clicking the noise reduction feature on each clip in the timeline produces this effect. But I've also tried clicking noise reduction on the entire video file in the browser and then adding the clips to the timeline. While editing, this seems to be much better, but when I render the video, it reverts to the same unwanted result. I've also tried creating a compound clip of the noise reduced clips that seem to sound good while editing, but again, same result when I render.

There has got to be a way to make this work correctly. It's frustrating, because when it is filtering the noise correctly, the audio sounds great. But this on/off/on/off effect makes it unusable. I have had the same results on my 2015 imac and my 2017 macbook pro.

Does anybody have a solution?