We are seeing an issue where composer is not properly installing a package, and subsequently the class is not available after deployment, causing errors.
Is there a way to clear the compser cache via the BitBucket admin?
Yes, it is possible to clear caches manually. You can go to this repo's page on Bitbucket website, then to Pipelines for this repo, and on the top right corner of the page that lists all Pipelines builds you'll see a link named Caches. If you select that, you will see all caches for this repo. Hover over the cache you want to delete, and you'll see a trash icon next to it that you can use to delete it.