Mailbox scrolling goes crazy on large inbox

I finally got Pandora working on a large Yahoo account; for it to get POP to work, I had to shrink Yahoo's inbox by archiving a lot of old messages, but I had it down to 33,000 or so. In Pandora, when I scrolled to the bottom of the inbox using the Windows scroll bar (right margin), it would jump right back to the top when I got to or near the bottom. The only way to see new messages (at the bottom) was to use the End button after clicking on a message in the list.

This went away when I moved a few thousand messages to an OldInbox folder. So my guess is that the scrolling function breaks at 32K messages. Maybe a signed 16-bit counter somewhere. This is on Windows 10 Pro.

Good find. Reproduced, fixed for September release.