Error Zero flow at top stage has nothinng to do with user added compoents. I suggest the following:
1. Try and change the number of stages . Note that mostly less than 6 the stages should be sufficient
2. Change extractant flow values 1 times feed flow till say 12 times feed flow
3. Try and change the temeprature
Reg Thermo ensure that there is immecibility as seen from LL env in RCM
You can also model it in Aspen 7.1 since you have it