Other basins do flow into the main drain.Do the other basins flow into the main drain.
Your kitchen waste might be plumbed into a rain water drain or soak way .
Try rodding back through main drain or take off the fittings in the kitchen and rod from there .
No soak away, but I'll check the main drains.
Nice thought, but I'm the one building the house, so it's effectively on meIf it is a new build get on to the house builder to fix it.