cracks in render

[Celt2]

Been waiting for several plasterers to come and take a look at some work we had done, none turned up yet and we need some answers!

Our rendering job on the gable end of our house was started by a qualified plasterer last September. Due to weather etc it's just been finished. One side is fine, but the other has quite a lot of hairline cracks in it. They were completed on different days. The plasterer has blamed our blockwork and says it has nothing to do with him , but can this be true when one half of the same wall is fine?

Some of the scratch coat did fall off, which he then replaced before putting on the top coat. It seems to sound 'hollow' in some places...also a channel that was dug out and repaired on another wall is also very obvious even though we have painted it.

It's a smooth render slightly textured with a sponge.

Is this impossible to hide?

Appreciate any help on this...