To give everyone an update on our situation. Strata homes have taken every ceiling out in the house and fit resilient bars across the joists. They have also layed fibreglass covering across the resilient bars. They have attached the plasterboard to the resilient bars and it has 100% cured the issue. The reason why it has cured the issue is that when they took the ceiling out you can see a slight bit of movement in the TJI joists when you knocked them gently. The resilient bars have clearly held the joists together more tightly which has solved the issues! Don't back down people, get your builders to fit resilient bars the way ours have! It worked![View attachment 367
How did you manage to get them to fix it. I'm at a loss, been fighting for 6 months now.