That's certainly not normal behaviour for Start11!
Can you let us know some more information on your settings please.
Is your start button centred or left aligned?
Are you using a custom start button image and if so what image?
Are you using the option in start11 to enhance the taskbar?
Are you using anything else which might have altered the taskbar in any way?
What scaling factor is your monitor set to?
Finally what build of Windows 11?