Problem: you cannot modify document in CRM. System says it is locked to to distribution. This situation persists for a longer time.

Solution: what has probably happened is that the replication process has failed at some point and system hasn’t been able to unblock the document. You can unblock it yourself in transaction SMQ2.

However, if this does not help there is a report called CRM_CHECK_DISTRIBUTION_STATUS which will allow you to list all documents currently blocked. It will also allow you to unblock all documents that are blocked but not being used.