I call C# function Process.Start which invokes mongorestore command. This command targets to a folder with backups created by mongodump command. The command sometimes fails and sometimes does not. The ratio is about 50:50.  When I run the exactly same command from command line manually, it works 100%.

The fail message looks like: Failed: census.Requisition: error dropping collection: ns not found. It looks like a collection is being dropped twice. If you inspect attached log, you can find example of this with ActionLogItem collection (see picture).

As I said, it fails randomly. It's not always the same collection, it doesn't fail all the time etc.