While replacing a node and during the recovery, the node did reboot (human mistake). After actual reboot the recover did not proceed and the node stayed in DOWN state, even if we tried to restart it via the admintools.

In vertica.log, we could see the following lines:

<PANIC> @v_dwh_node0003: VX001/2973: Data consistency problems found; startup aborted
 HINT: Check that all file systems are properly mounted. Also, the --force option can be used to delete corrupted data and recover from the cluster
 LOCATION: mainEntryPoint, /scratch_a/release/vbuild/vertica/Basics/vertica.cpp:1441

As the logs nicely suggest, using the (undocumented) --force option can help. That said, this option cannot be used from the admintool curse interface, and must be used from the command line:

/opt/vertica/bin/admintools -t restart_node -d $db_name -s $host --force

That way corrupted data was deleted, and the recovering could carry on nicely.