The locks are eventually removed automatically by cronjobs, if they don’t run properly, that can be an issue. If no redis cache is use for locking, it is handled by the database, and it can create such a huge load on the database, that it fails managing this properly.
You can remove the file locks manually from the database: File is locked - how to unlock
And shared hosting comes with limitations: How To: Get Help on Shared Webhosting