Thanks for identifying this.
Please put compensating formula into the driver software. It is important to have same linearity between short (i.e. flats) and (long (i.e. light) exposures.
The longer exposures also don't have intersection at 0,0 point in the graph if I do linear regression. So mathematically flat correction by light / flat no longer is correct. You need to apply correction to long exposures.
Thanks,
Gert