I've had to repair two Sierra Click mechanisms on Elegant Sierras. I don't have pictures to illustrate. There were two different issues, which I can't tell if they were mechanism or user errors.
Shine a flashlight down the barrel first. I noticed a cracked housing where it looked like the refill had (by user?) been jammed in and caused the crack.
You should be able to disassemble by stuffing a piece of paper towel down the barrel and tapping the mechanism out with a disassembly punch. Unscrew the metal click button, and you should be able to push the plastic mechanism out.
I was able to replace the cracked housing, which unscrewed from the plastic mechanism, with a spare.
On an earlier repair, the "clicker rocker" (I don't know what it's called, but it's a piece of plastic in a slot that allows the refill to extend or retract) was chipped. I was able to swap it for a spare.
Overall, this might help with the fix, but it doesn't solve or answer the question of durability. I'm becoming skeptical. I suspect if you contacted Berea, they would supply a replacement.