Hello Anastasia!
Thank you very much for your response! My bvecs and bvals were created by saving excel spreadsheet as a tab delimited file on mac. I reformated my bvecs manually using "nano" and reran the preprocessing. Unfortunately, it exited with the same error. I'm providing you my reformated bvecs...
I believe that the problem is not in reading of decimals, because running this step with "fake" bvecs of 1s and 0s (test_bvecs.txt) produces the same output with zeros, and everything seems to be ok with the tutorial dataset... What would you suggest? --- Best Regards, Alex