I get very different results when I make my geometry from one part only, and when I make 2 parts and connect them together. Anyone hwo knows why these could be?
At the interface of two tied parts you'll get some error there as the displacements at nodes of disimilar geometry are interpolated. Otherwise the results should be fine. Check to make sure you've connected them properly by plotting dispalcements as contours. The plots should be continuous.
Try to use surface to surface Tie, it could give you slighty better answer.
However, it is always advice that you should try to avoide using tie near to the area of intrested.