I finally dialed in a nice low action on the Warwick Streamer Pro
when fretting a A#/Bb, I found a single buzz on the E string at the 5th fret
(the fret behind the 6th fret note).

Seems the end of the fret has lifted a bit from the Wenge board.


Questions:

1. What causes fret ends to lift?
2. What would be the best way to fix this?
3. Can it be prevented from happening again?

Any help would be appreicated.

This is a good question. I have seen a bit of this on some basses, even nicer, high end models. Always thought it was due to fretboard contraction, but I have no idea. Can it be fixed easily?

Consider this a "bump" post.

What a useful question.

Wonder why it hasn't been answered yet?

wrap a tap hammer head in duct tape and gently tap it back down.

If it lifted, it's probably not very well seated in the wood. That is, the tangs are not keeping it stuck and the fret wants to go back to being straight.

It happens. Tapping it in may or may not be a lasting solution. If it pops back up, you will need to use some super glue in order to keep it down.