MongoDB index failing to create/build - mongodb

Question

There was a related post which states it was fixed in 4.x but I'm facing this error with stable 6.0.2 as well.
Index creation:
Enterprise rs0 [direct: primary] bs> db.keyvalue.createIndex({"key": 1},{unique:true,name: "kv_key_idx"})
kv_key_idx
BUT, only the default index is present:
Enterprise rs0 [direct: primary] bs>
Indexes for keyvalue:
[ { v: 2, key: { _id: 1 }, name: '_id_' } ]
From the logs:
{"t":{"$date":"2022-11-02T12:46:02.500+00:00"},"s":"I", "c":"INDEX", "id":20438, "ctx":"conn919","msg":"Index build: registering","attr":{"buildUUID":{"uuid":{"$uuid":"d1c79715-78e7-4e4d-ae7b-af96be6b3a6b"}},"namespace":"bs.keyvalue","collectionUUID":{"uuid":{"$uuid":"f168d08c-6182-4b89-935c-cf2564bd184d"}},"indexes":1,"firstIndex":{"name":"kv_key_idx"},"command":{"createIndexes":"keyvalue","v":2,"indexes":[{"unique":true,"name":"kv_key_idx","key":{"key":1}}],"ignoreUnknownIndexOptions":false}}}
and it very much is failing:
{"t":{"$date":"2022-11-02T12:46:02.516+00:00"},"s":"I", "c":"INDEX", "id":20448, "ctx":"conn919","msg":"Index build: failed because collection dropped","attr":{"buildUUID":{"uuid":{"$uuid":"d1c79715-78e7-4e4d-ae7b-af96be6b3a6b"}},"namespace":"bs.keyvalue","collectionUUID":{"uuid":{"$uuid":"f168d08c-6182-4b89-935c-cf2564bd184d"}},"exception":{"code":26,"codeName":"NamespaceNotFound","errmsg":"Caught exception during index builder (d1c79715-78e7-4e4d-ae7b-af96be6b3a6b) initialization on namespace bs.keyvalue (f168d08c-6182-4b89-935c-cf2564bd184d). 1 index specs provided. First index spec: { v: 2, unique: true, key: { key: 1 }, name: \"kv_key_idx\" } :: caused by :: Collection not found: config.system.indexBuilds"}}}
The db & collection is very much there:
Enterprise rs0 [direct: primary] test> show dbs
READ__ME_TO_RECOVER_YOUR_DATA 40.00 KiB
admin 80.00 KiB
bs. 2.13 TiB
config 168.00 KiB
local 59.85 GiB
Enterprise rs0 [direct: primary] test> use bs
switched to db bs
Enterprise rs0 [direct: primary] bs> show collections
keyvalue
Enterprise rs0 [direct: primary] bs> use local
switched to db local
Enterprise rs0 [direct: primary] local> show collections
oplog.rs
replset.election
replset.initialSyncId
replset.minvalid
replset.oplogTruncateAfterPoint
startup_log
system.replset
system.rollback.id
system.tenantMigration.oplogView [view]
system.views
What am I missing here? Thanks!