While doing a pre-hike gear-check I discovered why my LT4s where suddenly giving me locking problems. In 4 years of use and abuse they have been solid and reliable. But then - Yat-te-Hey?
Check out those threads. The one on the left is how I found it. The one on the right has been cleaned.
The threads were filled with expander detritus, generated over the years of loosen/tighten.
And now they are back to normal.
Oh - as long as you are in there, swab out the upper.