[ToME 1.5.10] Disappearing scroll bars in level up screen

[BugReporter]

Short description.
Scroll bars in level up window doesn't reappear after moving the cursor over some UI elements.
Actual result.
Scroll bars doesn't reappear.
Expected result.
Scroll bars should be visible.
Steps to reproduce.
1. Open "level up" window.
2. Move the cursor to the generic talents column so that the scroll bar appears.
3. Move the cursor over "Generic points: X" (the scroll bar should disappear as expected).
4. Move the cursor back to the generic talents column without crossing any other column (the scroll bar doesn't reappear).
Game version.
1.5.9 and 1.5.10 for windows from ToME site.
Comment.
It works for combinations of class and generic talents columns with "Stats: X", "Class points: X", "Category points: X", and "Generic points: X".
Neither "Inscriptions" nor "Prodigies" cause the issue. But those are actually buttons that open other windows.