In an configuration with multiple databases, if records are inserted into collections of one database, records from unrelated collections may be "inserted"* into yet other unrelated collections. There may also be rearrangements in collections in the original database, but I can not determine this as readily as all records in the same database have an id of the same name so I have been using {id_name: {$exists:false}} to find the errors.

The logs frequently show errors indicating a bad BSON object type and extremely long strings. Further, validate does not always find the errors and returns 'ok' when errors are still present.

Other than inserting a couple hundred thousand records into a couple collections at the same time with the Java driver, I have not found a specific way to reproduce this error, but I can provide a valgrind log

*The bad records do not seem to be inserted with any client insert calls and the journal file does not repair the collections