Limit to number of fields that can be exported?

I have successfully exported 23 phenotype data fields to play around with while getting my pheWAS project started. However, I am interested in running many variables against my SNP of interest. My previous method for extracting the 23 sample phenotypes (using the dx extract_dataset bash command) did not work for exporting many additional variables. I have tried running the export in batches (500/250/100 variables at a time), but I continue to run into errors and timeouts. 

Is there a limit to the number of fields that can be exported in a single command? Surely someone before me has been interested in calculating the minor allele effect size for many different variables, not just a select few. 

Thanks for any help/insights.