I am the owner/admin of our site and I have 5 users who have access to edit/create documents in a Document Library. We are using Sharepoint online (Modern) and have not had this issue until last week. The error is only affecting 1 user out of the 5. All 5 users are creating documents the exact same way. The user has tried creating a new document online and has also tried creating a document in Word then uploading the document and she is getting the same error message. Does anyone have a solution besides waiting until it unlocks?
We run into the same issue and users didn't liked having to wait for SharePoint to release the lock on its own. This is a frustrating bug!
Possible workaround: The problem could also be because of reaching the limit of minor versions (511). Step 1: Publish a major version and check if that didn't solve the issue then try Step 2. Step 2: Download a copy and upload it again that will solve the issue as it solved for us.