I have also experienced this, often in open fields or areas obviously clear of zombies. Often the sound is cut off shortly.

I too have experienced this bug at one point. It lasted until the user in question logged out. Attempts to communicate via direct chat all failed.

Added a screenshot as requested. Steps to reproduce on my end:

1: Have flashlight out and powered on
2: Perform eating animation
3: There is now permanent flashlight beam emanating from where you were standing