Voltcraft/SkyRC (original) B6AC (v1) charger does work properly - calibration does not work, wrong current measurement

[fhvyhjriur]

I have a B6AC charger from Voltcraft. Voltcraft is a european company that order big volumes at original manufacturer and lets them relabel the original hardware with "Voltcraft".
I installed the B6AC atmega32 release from https://github.com/stawel/cheali-charger/tree/master/hex/unstable and have issues with current calibration and current measurement.
When i follow the typical calibration, i first calibrate the voltage. Then i calibrate the charge current and then the discharge current.
Issue immediately after calibration: I cant start charging. The error is "I Discharge 4". If i understand correctly, the issue is that when i was able to calibrate with the expected current setting, at first usage this calibration setting is used on a different way and then the calibrated value is too big and thus the charge cant start (even when i only select charge with no discharge).
After i understood this in that way i calibrated it "wrong". I set the expected 300mA discharge current to real/measured 250mA instead of 300mA. All other current calibration (both charge and 50mA discharge) was measured and calibrated correct.
Then i was able to start charging. But then i had to find out that the used charge current is completely off. Its around 40-60% instead of the chosen value in the charge-settings.

What can i do to fix this situation?

PS: I have not tried out the closed source software the device came with. I am not interested in using closed source software and replaced it untested with the cheali-charger release.