Agree with Dale’s assessment.
If his repair recommendation is beyond your skill knowledge set, I’d suggest you post a new topic - something like “Need help fixing my BLF A6”. Explain the situation and what you need help for. Include a copy of (or a link to) DB’s post. You may find someone willing to do the work for no cost/low cost in your immediate area.
AFAIK, what happened to you is rare. What’s been reported by others is shearing off of the dome. The flashlights still worked, albeit with a more tightly focused beam and a slight shift in tint.
I think that if you read this discussion thread from start to finish, you’ll find some admonishments to be VERY careful when unscrewing the head. Not that this is your fault, it was just an unfortunate manufacturing choice to use a square die and a square centering ring. I understand that some of the later models had this flaw corrected by using a circular die and a circular centering ring. Here was my solution: Bare BLF A6 Interest List (coupon now public)