whilst thinking I was going to restring my H50 Orchestra electric Jazz guitar bought at Eatons in Victoria 77 years ago I decided to clean the neck up prior to regluing the banding that was coming undone at near pickup on neck itself.
Cleaning the old glue I noted I saw the fret board move and moments later come right off the neck, fully, and completely
The guitar was unplayable above about 8th or 10th fret, probably due to a lifting fretboard and still reasonable below the 10th.
I seldom play it but was time, as is custom every decade to renew the strings. This decades choice D'Addario XL ECG24 Jazz Light flat wound 11/50s.
I'm no stranger to guitar repair and set up.
but
with fretboard completely off I began to light sand and clean old glue on both neck and backside of fretboard itself when I noticed that the fingerboard itself at the 3rd fret is cracked side to side along fret underside and is only held together by the banding..I was going to glue.

The fret board is a 14" radius, 1.650" at nut and 2.25" at about 20th fret. The board has 19 frets though is about 20 frets in length.

So, what would you do?