CalibrateSDR with HackRF

[apppie123]

I'm trying to resolve an intermitted issue with my HackRF device so I thought about trying to find the crystal accuracy and if my cheap chinese 0.1ppm external crystal might have drifted.

To record data from the HackRF I'm using:
hackrf_transfer -r test.iq -f 220352000 -s 2048000
call hackrf_set_sample_rate(2048000 Hz/2.048 MHz)
call hackrf_set_hw_sync_mode(0)
call hackrf_set_freq(220352000 Hz/220.352 MHz)

I let it run for about 30 seconds.

Then I run CalibrateSDR:
python3 cali.py -f test.iq -rs 2048000 -v
{'f': 'test.iq', 'm': 'dab', 's': 'rtlsdr', 'c': 'all', 'rs': 2048000, 'rg': 20, 'rd': 0, 'nsec': 10, 'graph': False, 'verbose': True}
let's find your SDR's oscillator precision
loading file...
starting mode: dab
your sdr's precision is None ppm

However I'm getting a response of "None". What could be the issue?