Shelly Dimmer 2 calibration fails after firmware upgrade - can I downgrade it?

I have a dimmer 2 controlling a ceiling light. The dimmer has been working perfectly for 6 months. Yesterday, after the firmware upgrade, the app asked to calibrate the light again, and unfortunately it seems that it is not possible to calibrate it anymore.

Is there a way to calibrate it? Can I rollback to the previous version of the firmware?