A collection cannot be capped and clustered
What changes in A collection cannot be capped and clustered compared with MongoDB and what your application has to do.
This difference is of the Different kind.
What MongoDB does
It allows it with enableTestCommands.
What TeselaDB does
It always refuses it with error 6127800, also with convertToCapped on a clustered collection.
What your application has to do
Choose one of the two collection types.