Cancel Downgrade button returns 404 error

When downgrading a plan on Bitbucket, it would say "Downgrade will be processed at the end of billing cycle" and you will have an option to downgrade the button.

Clicking the downgrade button leads to a 404 Error. The button redirects to an invalid URL

https://bitbucket.org/account/user/<USERNAME>/upgrade/undefined

Current Workaround

• Navigate to Bitbucket Account Settings and upgrade the account plan.