An error in the sum of three signal

I just use sum of three signals and i get an error like this. Can you help to rectify this error ?

Answer 1

[Charanraj]

Answer 2

[niklasnylen]

The error says it's an algebraic loop. Do you feed any signal back in the model. If that is the case you should add a Memory or Unit Delay block on the feedback signal line.

Answer 3

[Charanraj]

Seems adding a memory makes more complications, which I have attached in the picture. And there are many unit delay blocks. Which one do you recommend and the configurations of it will be default or any user defined ?