In cases like this, you’ll want to hunt down the offending modules in task manager and terminate them individually. The error message indicates that BL is running somewhere. I’d look for Bambusource.dll as a probable culprit.
However, one utility that is particularly good at remedying this exact problem is Revo uninstaller. Make sure you create a system restore point before you run it. Revo typically will warn you.
Be careful which link you click on when downloading. You want to download the free version(it’s really trialware or nagware).
After it removes all vestiges of the product you want uninstalled, try reinstalling Bambu Studio and ensure that it is working. Reboot twice just to be sure. Then, uninstall Revo Uninstaller as it has done its job and becomes annoying nagware with constant prompts to purchase the product afterward.