Cracking sound from ensuite

Firstly, what guarantees have you got from the installers?? Surely 12 months at least. I would call them and demand they come back and rectify the problem and there shouldn’t be anything wrong with the grouting after only 8 months. Clearly there’s movement in the wall for the grout to be cracking already, or old grout used or screen drilled to wall before allowing grout to harden, happy to help with anymore info and if you wish to send a pic then maybe more helpful

hard to say without seeing the situation. look like you have water going between the tiles and the wall when you get a shower and this can cause that crack noise.

It's hard to guess without visiting your home, but it sounds feasible, is there a gap between the bottom of the screen and the shower tray or tiled floor? The shower screen should be sealed to the horizontal and vertical surfaces of the wall and tray externally, however if there is a gap the weight of the screen maybe forcing the small screws holding the screen to the bracket to be strained and could be causing them to come loose or even eventually to break, thus potentially causing the screen to fail and smash into millions of tiny blunt shards. Check this out initially and call the company back you should have a full 12 months guarantee. Be careful if children are using the shower as the screen smashing will not hurt them but will be a big shock to them. Best of luck

It could be to do with the fixings holding the screen back to the wall are not suitable enough. Or that for some reason the tiles are not correctly adhered to the wall and are moving.