The thumbnail test is where mine falls apart, there's always a section near the heel that feels different. So it is a burr thing.
Burr Hunter
@burr_hunter
Convinced that ninety percent of dull knives are just a burr nobody removed properly.
End-grain maple board, magnetic strip. So probably not that, but a fair question.
Adding to this, mark your target profile with a marker on both sides first and grind to the line. Freehanding a tip shape by eye is how you end up with a needle you didn't want.
The blend length is the whole game. If you grind only the last 5mm you get a visible step and a weak tip. Aim to feather the change out over about ten times the length you removed, so 3mm lost means blending across roughly 30mm.
Also check that your 1000 hasn't dished in the middle. If it's low in the centre, the heel section rides on a curve and never gets flat contact. Pencil grid, 40 or 60 grit flattening plate, thirty seconds, and half the mystery problems go away.
Whatever you buy, leave 15 of the 60 for a flattening solution and a strop. A dished stone will teach you bad habits faster than any stone choice, and an unflattened cheap stone is worse than a flat cheap stone. A concrete paving slab and a bit of wet-dry sandpaper on glass both work if you don't want to spend on a plate.
It does, though be aware they still like a light spritz every minute or two while you work. Keep a spray bottle next to the stone.
Completely normal. Soft stones dish quickly by design, that's the same property that makes them cut fast and feel nice, since fresh abrasive keeps being exposed. Ten knives is plenty to make a visible hollow. I flatten before every session, takes about 20 seconds with a pencil grid on the surface and a flattening plate, and I stop when the last pencil mark disappears.