Sadly it does happen periodically with clicky switches.
I am not sure how long they have offered this but you can call fenix-store for an RMA or warranty repair... hopefully that's where you bought it from.
https://www.fenix-store.com/information.php?info_id=5
********************************************************
NO QUESTIONS ASKED LIFETIME WARRANTY
We have a new policy for all Fenix brand products. We are so
confident in these flashlights that we are now upgrading all Fenix
lights purchased past, present, and future to an unconditional
lifetime warranty.
We will repair or replace any Fenix lights purchased from
http://www.fenix-store.com/. Simply go through our "contact us"
link to initiate the RMA process. Your light will be return fully
functional. The exterior finish is not covered as this is cosmetic
and does not affect the function. If your model is discontinued,
we may issue you store credit or offer you a newer model of
equal or greater value. We reserve the right to issue a
refund in lieu of a replacement.
The only requirements are:
1) A Fenix brand product purchased from
http://www.fenix-store.com/
2) You must supply proof of purchase. An order number
that matches your contact information is sufficient.
3) You must got through the standard RMA process where we
will try to diagnose your problem before asking you to send it in
****************************************************
I would go this route before taking it apart or attempting a DIY repair.
