I have not reproduced the problem. It may depend on Settings > Display Method and the GPU and its driver on your system.
There are 3 keyboard shortcuts for Remove: X, Shift+Delete or Shift+Backspace.
You can also click - on the timeline toolbar.
If you are trying to remove a blank, move the playhead over it, and press Ctrl+Space to first select it followed by one of the above.
There is no keyboard shortcut for Detach Audio, but here is how to do what it does:
- add an audio track if needed
- double-click the clip to select it and seek to its beginning
- copy the video clip Ctrl+C
- press Down as many times as needed to make the target audio track current
- overwrite the clip on the audio track B
- select the video clip
- in Properties > Audio, set Track to None