Terrible managing the return of our deposit

We were renting a property for 5 years through Connells and the management and communication regarding check out and return of our deposit was terrible.
We left the property in a very good condition considering we lived there for over 5 years with two small children, and if I was the landlord I would be very happy. The property was let two weeks after we left so it can't have been terrible.
The checkout was done by an "independent" company. However I am not sure how independent they are as they told us they only work for Connells. Anyway, the checkout report was reasonable although they tried to charge us for it.
We didn't hear anything for weeks and only after putting in an official request issued by the DPS we had a reply from Connells.
The landlord than proceeded to claim for things which were either already mentioned in the check in report as brokeb or not in the check out report at all. Surely Connells should have checked and made the landlord aware of these things before forwarding it to us. Both look like fools now.
Secondly, the costs for the claims were not broken down. We were just presented with an overall figure. Staggering for a so called professional company unless they were intentionally try to screw us.
Connells also didn't seem to be familar with the DPS claim procedure which we had to explain to the person. I don't have any trust in this agency and will stay very clear of them in future.