Using the Cut Time function on a locked clip will cause Pro Tools to crash on macOS. I've tested this with PT2018.4 on both macOS 10.12 and on 10.13 with the same result.
STEPS TO REPRODUCE:
1. Create a new audio track.
2. Create a new clip through consolidate.
3. Apply Edit Lock on the clip.
4. Make a Timeline Selection within the clip.
5. Use Cut Time.
6. Click Allow to confirm.