Data from Oracle DB is not loaded in some cases

I have noticed that in some cases the data from Oracle DB is not loaded, but there is no exception in the Server as well, eventhough there are entries in DB.

I am using the configuration and data from the issue JDG-6591 . I was using ojdbc11.jar driver and oracle18cR3 instance in our RH DBAllocator.

It is reproducible with gen_md_bank.sql and according .proto file from the issue JDG-6591. When I reduce the number of columns and remove the _ sign from column names, the data is loaded properly. Then adding "_" to the names of the columns gradually, still the data is loaded, but then in some point, the entry returned by REST call is empty and there is no exception in the logs.