Dear @S3,
Welcome back to the Wefugees Community and thank you for reaching out to us.
I am not aware of possible complications when you are travelling and returning to Germany with a valid residence permit which expires soon. But I will ask my dear colleague @mbeon-Éanna as well to be sure.
However, I hope you are aware that a German temporary residence permit usually expires automatically after being abroad for more than 6 months (you are not holding a Blue Card but a "Blue" refugee passport, right?). Exceptions can be made but you always have to apply for it at the immigration office in advance.
Looking forward to your reply and all the best,
Meike