MongoRocks fails to repair if metadata is inconsistent with dropped idents (assumption)

Original report:

Last week after a restart of a Azure VM my Percona MongoDB working with RocksDB engine stopped working properly...
I tried with --repair but the result is the same. Can anyone help?

OS: Ubuntu 16.04
Filesystem: [/sbin/fsck.ext4 (1) -- /datadrive] fsck.ext4 /dev/sdc1

2017-08-20T22:03:11.997+0000 I CONTROL [main] ***** SERVER RESTARTED *****

2017-08-20T22:03:12.005+0000 I STORAGE [main] [RocksDB] Block Cache Size GB: 0

2017-08-20T22:03:12.005+0000 I STORAGE [main] [RocksDB] Compression: snappy

2017-08-20T22:03:12.005+0000 I STORAGE [main] [RocksDB] MaxWriteMBPerSec: 1024

2017-08-20T22:03:12.005+0000 I STORAGE [main] [RocksDB] Engine custom option:

2017-08-20T22:03:12.005+0000 I STORAGE [main] [RocksDB] Crash safe counters: 0

2017-08-20T22:03:12.005+0000 I STORAGE [main] [RocksDB] Counters: 0

2017-08-20T22:03:12.005+0000 I STORAGE [main] [RocksDB] Use SingleDelete in index: 0

2017-08-20T22:03:12.008+0000 I ACCESS [main] Initialized External Auth Session

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] MongoDB starting : pid=20429 port=27017 dbpath=/datadrive/mongodb 64-bit host=hiddenOnPurpose

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] db version v3.2.15-3.5

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] git version: 3615e6f7425b87278261a9f2d3e52a14ff3c2a46

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] OpenSSL version: OpenSSL 1.0.2g 1 Mar 2016

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] allocator: tcmalloc

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] modules: none

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] build environment:

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] distarch: x86_64

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] target_arch: x86_64

2017-08-20T22:03:12.015+0000 I CONTROL [initandlisten] options: { config: "/etc/mongod.conf", net:

{ bindIp: true, port: 27017 }

, processManagement:

{ fork: true, pidFilePath: "/ var/run/mongod.pid" }

, security:

{ authorization: "enabled" }

, setParameter:

{ failIndexKeyTooLong: "false", internalQueryExecYieldIterations: "100000", internalQueryExecYieldPeri odMS: "1000" }

, storage: { dbPath: "/datadrive/mongodb", engine: "rocksdb", journal:

{ enabled: true }

}, systemLog:

{ destination: "file", logAppend: true, path: "/datadrive/log/ mongod.log" }

}

2017-08-20T22:03:12.067+0000 W - [initandlisten] Detected unclean shutdown - /datadrive/mongodb/mongod.lock is not empty.

2017-08-20T22:03:12.293+0000 I STORAGE [initandlisten] 126 dropped prefixes need compaction

2017-08-20T22:03:12.332+0000 I STORAGE [initandlisten] dropping unused ident: index-0--421938426481405637

2017-08-20T22:03:12.381+0000 I STORAGE [initandlisten] dropping unused ident: index-1--421938426481405637

2017-08-20T22:03:12.496+0000 I - [initandlisten] Invariant failure prefixIter != _identPrefixMap.end() src/mongo/db/storage/rocks/src/rocks_engine.cpp 501

2017-08-20T22:03:12.496+0000 I - [initandlisten]

***aborting after invariant() failure

2017-08-20T22:03:12.535+0000 F - [initandlisten] Got signal: 6 (Aborted).