Can not drop db in sharded environment I am trying to delete some old dbs in my sharded set up.
Step i am taking are :


Stop Balancer.
Drop Db
Start balancer


But in some of the DBs i am getting these errors.

"errmsg" : "exception: collection's metadata is undergoing changes. Please try again."

"errmsg" : "exception: Error locking distributed lock for chunk drop. :: caused by :: 13661 distributed lock ibeat20140904.dgrpCount/iBeat55:27017:1420803001:1804289383 had errors communicating with individual server x.x.x.x:27017 :: caused by :: field not found, expected type 7" 


When i checked the db using show collections some of those collections were removed but not all.
 x.x.x.x:27017 is ip of my config server.
I check hash of all config servers and they seems to be in sync.
Looks like this is similar to: https://jira.mongodb.org/browse/SERVER-17243
This is not fixed as of November 16, 2015.
From the link:

Description
After dropping the collection for a sharded collection, via mongos, the chunks are still visible in the config server. Same if the database is dropped.
This collection had balancing failures, which seems to have left a lock in place, preventing full cleanup.