What type of wall construction do you use? Which boundary conditions does it face?

Does the same error message occure when you use a different construction for this zone? Have you tried to plot the outside temperatur of that external wall on a online plotter? It seems that the wall is facing high loads (either external or internal) which stack up over time.

General things to check: - thermal properties of the layers and materials (e.g. conductivity) - Time base setting as deafult (1) - internal loads and gains

Does the same error occurs when you set an outside boundary condition e.g. 20°C for that wall