Discharge pipe temperature error (F3-00)

[gaumin]

Altherma 3. Once the outside temperature dropped below zero (0°C to -4°C) I started encountering an error "F3-00 Malfunction of discharge pipe temperature" at the end of the DHW operation cycle. The DHW setpoint is 50°C. Upon checking the logs, I noticed that the refrigerant temperature almost reached 120°C, which appears to be critical.

I’m wondering what could be the cause of this issue. Could it be due to a low level of refrigerant?

Additionally, I’d appreciate it if someone could share their "Discharge Pipe Temperature" and "Refrigerant Pressure" historical graphs during DHW operation. I’d like to understand the acceptable range for these metrics. Thanks!