After the introduction of additional character slots per server in TBC Classic, the character name you click on the character list often (but not always) actually gives you another character’s preview.
So basically, if you clicked on Character4 for example, it shows you Character5 on the screen. End result being that if you double click a toon to log in, you log in as a wrong character.
I play on windowed mode, and do have characters over the visibility limit which means I am scrolling back and forth at times.
Repro steps with windowed mode, not full screen:
1.) Launch game
2.) Log in with character 1 (the one on top)
3.) Logout
4.) Scroll down and log on to character 10, which is the first one that requires scrolling in order to access
5.) Logout, and you will have the bug: a different character is being shown than the one which is selected in the character list
It seems like it resets the view back to the top with 9 characters shown (which do not require scrolling) and selects character 9 from the list automatically even though you just played on character 10.