I had a Duravit wall mounted toilet installed this summer along with a walk in shower with a floor drain. Recently we noticed that the toilet does not flush completely. It has not overflowed. Twice I noticed that water was gurgling in the floor drain in the shower too. Used a snake in the toilet but it didn't help. There is a Studor 'mini vent' on the wall next to the toilet. Could there be an issue with the venting? Thanks!