Are you saying that when you use the audio visualisation you can’t size and position it where you want on screen like is shown in the screenshot below?
If that’s your problem, you don’t need to use the S&P filter at all. You can resize and reposition the AV filter from within it’s own dialogue. A box similar to the S&P filter appears with an anchor in the centre you can use to drag it and resize using the corners. The screenshot below shows the filters used on that clip and, as you can see, no S&P and the box for the AV filter is visible.
If that’s what you’re already doing, then if it is a bug, maybe it’s specific to the version you are using. You might need to look at your project or reinstall Shotcut with a newer version. The images above came from version 18.11.13 (Windows)