I do consider Biogen to be a large cap stock, not generally volatile.
A large cap stock can have events that significantly affect share price, such as the Aduhelm spike and drop.
That event was short term and there was no shortage of shares to borrow. At present the interest rate to borrow $BIIB shares is .25% and that's in context of a very different interest rate regimen compared to when the Aduhelm situation unfolded.