Found NULL Node in GraphObj array.

Well. Unreal crashed, just a little crash, and I had saved often prior.
But for the second time today a crash has robbed me of work. Nodes inside a compiled and saved blueprint disappeared and had to be remade by hand.
Now I’m getting this message repeated (10 to 15 times) in the log each time I save:

LogGraphPanel:Warning: Found NULL Node in GraphObj array. A node type has been deleted without creating an ActiveClassRedictor to K2Node_DeadClass.

The blueprint SEEMS to be functioning correctly, but I am concerned this is indicative of something deeper that will come out to play later.

Additionally, I’m now getting this message each time the blueprint constructs:

LogScript:Warning: Accessed None 'CurrentRoom'

‘CurrentRoom’ being the name of my variable. I’m still combing through my graph to find the source/s but any help would be greatly appreciated.

If you need more information/screenshots let me know what you need and I’ll post them as soon as possible.