This offset issue with ASI178MM reminds me of the noise reduction done by Canon DSLRs, where the dark current behavior is odd .
It looks like all Sony EXMOR sensors have this non-linearity issue (due to the noise reduction they implemented?), requiring raising the offset value, according to this Cloudy Nights thread . But, they also suggest disabling the ampglow reduction feature, that I only found references for the QHY5III178M.
Do you know if the ZWO/ASI INDI driver has this ampglow reduction toggle?

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