Buderus Logamax heating problems

Hello everyone, I own the Buderus Logamax GB132. For some time now, the error 3C 217 has been appearing. This can be reset and the heating then works again for about 2 weeks. The problem is that, in my opinion, when the error occurs, the fan continues to run at full speed even though the heating has shut down and also becomes cold. Only after rebooting does everything run normally again. My concern is if no one is at home for a longer period. The fan seems, although the error is present, not to switch off by itself but to continue running at full speed. What happens then? By the way, the fan was also recently replaced or renewed. According to my research on the internet, it could also be the UBA combustion controller? Are there possibly other causes? My heating company also seems to no longer know how to proceed regarding this matter? The Buderus customer service no longer accepts orders from private customers either. Maybe someone has already had experience with this and could help me? Thanks in advance! Best regards