As is the case with other MacOS add-ins, I find when running BST causes Notification Centre to become unresponsive (and use 100% CPU). Many other reports of this, and many of them seem to be related to other 3rd-party add-ins. Otherwise BST seems to work fine 
I noticed this emerge with Big Sur.
I haven't seen something like this yet, in which situations does this happen?
It happens all the time - after running BST for 30 mins or so? See this thread which mentions other user experiences of BST: https://www.reddit.com/r/MacOS/comments/jtnclh/notification_centre_keeps_freezing/
Some implication of utility Tiles as well.