I have a model, imported as a stp file that is giving me problems. There are faces that I need to extend or delete and I cannot do either. The extend face command gives me a message 'the extended faces are not connected' and the delete face command gives me a message that it will resulting in a vertex with more than 2 converging open edges. Does this sound like a fault with the original model, the way it's imported or the software? (SW 2015)