The toilet does not flush completely clean

Hello, we have a new toilet (pressure flush, siphonic toilet). However, it does not flush completely, i.e. the front part remains almost dry, to flush away the last paper, you have to press x times. Is this a defect that can be claimed? What can be done? Thanks!

Good morning

You have only replaced the WC and flush valve?
The pipes are old and possibly galvanized steel pipes with deposits?
It is possible that the minimum flow pressure and the necessary water quantity are not available.
It is also possible that deposits loosened when the water was turned on and settled in front of the flush valve.

I do not see a claimable defect in these cases.

To avoid such errors, I would have converted to a cistern.

Olli