Invalid ID during netcdf writing

I am new to netcdf files, and trying to write a file containing geophysical data. I have 600x2158 datapoints, but each column has a set of coordinates, so my final matrix should be 600x2158x2158. This is large, so I wrote it as an ndSparse matrix. My error arises before I even try to write the ndSparse matrix of my data into the netcdf file. When I try to write the vector of y-coordinates (2158 positions) into the netcdf file, I get the following error:

Error using netcdflib

The NetCDF library encountered an error during execution of

'putVarDouble' function - 'Not a valid ID (NC_EBADID)'.

Error in netcdf.putVar (line 88)

netcdflib(funcstr,ncid,varid,varargin{:});

The same happens if I try to write the 600-position z-vector, or the 2158-position x-vector.

If I try to write the ndSparse data matrix, I just get an error saying the format isn't recognised, so I need to find a solution for that too!

Thanks in advance!