The error you are seeing suggests that the NFS mount is being used by several processes at once and that there is a locking problem on the NFS server, as stated in the comments.

Please be noted that LevelDB is designed to be used by a single process at a time. When you are trying for multiple processes this could also be done by using kubernetes mechanisms like Pod Affinity or Pod Anti-Affinity to make sure that only one pod can access the database at a time.

Adding to that you can also use the Pod Topology Spread Constraints which might help to resolve the constraint issue.