After running analysis, the Staad Output didn't inform me of instabilities in the any joint. In the post-processing mode I clicked on nodes-instabilties and noticed that I had two nodes that were unstable. I have attached the model. I believe my releases are correct.
There were two pairs of nodes (406, 508) and (410, 506) which were within a very close proximity of each other. I merged these keeping first one in each set and the model now analyzes without any instabilities. A modified file is attached for your reference.
Answer Verified By: Catherine Stanley
Structure2_modified.std