scrollbar's thumb disappearing

[Nicolas Cueto]

Hello All,

Odd behaviour. Two vertical scrollbars, both the same size and settings, but
differing in name, end value, script and the card they belong to. As well,
neither scrollbar belongs to a group.

Problem is, when I click on the bar of one scrollbar, its thumbnail almost
always "disappears", i.e., the value is still visible and the script runs
fine but the thumb itself disappers. Click-dragging the thumbnail also
causes it to disappears (or even half-disappear), but less often than as a
result of clicking on the bar. The other scrollbar works no problems.

Any ideas why this is happening? I tried fiddling around with the stack's
buffer display setting, as well as resizing the scrollbar. But...

As always, thank you in advance.

Cheers,
Nicolas Cueto
niconiko language school