Answer:
In this case, you can try to adjust the FE mesh to be finer.
However, it is usually better to regenerate the model and to round off the node coordinates to 6 decimal places, for example. You can access this feature using the menu "Tools → Regenerate Model". This way, the inaccuracies caused by the smallest differences in a coordinate are corrected (see Image 01).
The model check can also find double nodes (menu "Tools → Model Check → Identical Nodes"). In the following dialog box, you can specify what is to happen with these nodes (see Image 02).
