Pre-Cast Flue - Crack up wall

[ImperialHammer]

We have a pre-cast flue for a now removed gas fire.

There is a crack that runs up the length of the flue on the left side. It starts at the top of the old fireplace hole and continues upstairs ending at the ceiling.

Is this a sign of a more serious issue or just normal expansion/ contraction from temperature differences?

 

[^woody^]

Yes, shrinkage and common for flue blocks within a single cavity wall leaf, not so common for flues sections within a chimney flue.