I've stumbled across a weird glitch in the vertical scrollbar for a dialog list control which seems to be affected by whether the number of items in the exceeds 65535 by a few/many.

When you try to drag the scroll focus downward, it will snap right back to a position near the top. Sometimes, if you hold the scroll focus in the middle for a long time, it will stay there when you let go of the mouse. But if you then grab the scroll focus again, the view immediately shifts to the top again, and the scroll square will bounce back up to the top again.

It's usually affected, but not always, by whether the number of items in the list exceeds 65535, and sometimes is affected by what's the total number of items loaded into the control the 1st time. I've even managed to start it with the glitch being gone at rows=65534, and then have it show up after manually adding fewer than a dozen additional rows.

The example re-creates a hash table and reloads the list control each time you click on 'create', but it's lightyears faster to load the dialog list using $hfind than to have a loop which adds them one at a time.

Code
dialog biglist {
  size -1 -1 200 200
  option dbu
  button "create (slow)",3,6 100 50 20
  list 6, 101 11 70 62
}
on *:DIALOG:biglist:sclick:3:{
  did -r $dname 6 | hfree -w test | var %i 1
  while (%i isnum 1-65534) { hadd -m1 test $+(item,%i) $+(data,%i) | inc %i }
  noop $hfind(test,*,0,w,did -a $dname 6 $1 )
}