A Horrible Game Breaking Bug!

Okay, I was playing a customized world on Snapshot 15w35b and was building something complete with stairs and a door and when I saved and quit, and then I came back, and the stairs are gone and only half a door remains which is buggy and unresponsive,. I have included a screenshot as evidence, oh yeah, and afterwards commands are unresponsive and just gave me a red text error.