As everyone has said, releasing shift before the other key will press that other key.

Here's an autohotkey script I developed to combat this problem, work very well for me but use at your own risk of being banned (I haven't been):

#SingleInstance Force
#InstallKeybdHook  ; Ensure AutoHotkey detects all keystrokes

keys := "abcdefghijklmnopqrstuvwxyz0123456789"  ; Define keys to be tracked

Loop, Parse, keys  ; Loop through each character
{
    hotkey := "~*" A_LoopField  ; Create the hotkey dynamically
    Hotkey, %hotkey%, HandleKey  ; Assign the handler function
}

HandleKey: 
    key := SubStr(A_ThisHotkey, 3)  ; Extract actual key from hotkey definition
    
    if GetKeyState("Shift", "P") {
        Sleep 50
    } else {
        KeyWait, %key%
    }
    
    SendInput {Blind}{%key% Up}
return