SLC pre-processing problem

Dear all,
I am looking to pre-process Sentinel 1 IW SLC data before I implement the H-Alpha decomposition and Wishart classifier.
My processing chain is:

  • S-1 TOP split
  • Deburst
  • Orbit file
  • Subset
  • Radiometric calibration (complex output)
    but when i do the radiometric calibration step by the SNAP6.0,it failed as the picture
    but when i do the same step in SNAP5.0 ,it run successfully.
    i want to know why it requires to do caliberation before deburst?