The automated design will check for all parameters too specified in the design criteria. It is possible that with the design you are expecting with a particularly milder slope (0.0041 m/m) there could be violation of the velocity criteria. So in such cases although the slope and cover criteria might be fulfilled the velocity criteria might be violated.
Additionally, in the model you have specified tables for your criteria for all the diameters used. In the "Part Full Design" you have specified individual diameters but the percentage is same for all the diameters i.e. 65%. You can simply use 65% for the network and not include diameters. This can help simplify the model.
As we have stated, the automated design or constraint based design gives you a starting point for your design and not the final output because it is not always possible to fulfill all the design considerations for all the elements to be designed. See the article below on troubleshooting automated design results which can help you;
Troubleshooting Automated Design Results
Hope this helps.
Bentley Technical Support
As I mentioned from your product Help Document, Minimum Cover is the 6th priority and Slope and Velocity priorities are the next. Then what I expected was Automated Design designs the conduits with minimum slope to reach minimum Cover as higher priority. but it has been ignored and next ones (with lower priorities) were considered.
The ultimate objective of the automated / constraint based design is to try and get an overall balanced design as per the criteria set. It could be possible that while having a milder slope and less cover might fulfill the criteria for a particular conduit. But the effect of the same could be propagated downstream producing results which are not falling within the prescribed criteria.
You should understand that the design is for the entire system and the solver tries to find the best fit solution.
Nevertheless, the final design should be as per the engineer's judgement.