High -g- open string sustain question

High g question....

When played "open" the sustain is shorter (i.e. decays faster) than when played up the fretboard. There "is" some sustain, but I can best describe the sound as plunky or with a slight "thud".

Other strings played open have very good sustain and resonance, and when the -g- is played fretted 1-12 the sustain/resonance is similar to the other strings.

Strings = Worth Browns, well settled
'ukulele = Ohana CK 50G (concert, solid cedar top, solid rosewood back and sides)
bone nut and saddle
action @ 12th = 2.5
'uke is new (although build date is 2018)

I have searched and read a few dozen posts on the forum, however, most "thud, punky, dud, dead" threads deal with sustain deficiency when fretting.

String position/height in the saddle seems the same for all strings. I can't check the break point however, it's just too small .

Any suggestions or ideas?

Could it be the nut slot is a little wide, allowing it to roll or rub, and dissipating energy that way?

One thing that may be choking off the sustain is nut slot depth. If the G string is "buried" in the nut slot, vibration tends to be reduced. I like a shallow slot, i.e., the string protrudes at least 30% above the top of the nut. Also, the slot needs to fall away about 20 or 30 degrees towards the headstock so the string sits on the far front edge of the nut slot. Otherwise you can get some strange buzzes and harmonics.