Node reappear after deleted

I was hitting the "undo" (ctrl+z) multiple times and a console error caused shader forge to freeze up. Unfortunately, I didn't even read the console error, sorry. I reset Unity to the default layout to close shader forge. And upon reopening shader forge, I found about 4 or 5 copies of one of my previously deleted nodes.. the copies were just floating around the middle of my shader graph area, not connected to anything. They happen to be "code" nodes, but I doubt it matters what kind of node that are. I panicked, thinking my whole shader was probably wrecked. But after looking around at it (it's a big shader), I couldn't find anything else the matter with it, except these floating duplicates of that node. Since that node is one I already deleted, I simply deleted the mysterious floating duplicates. My shader worked fine, so I didn't think any more of it and went on with my happy day. But then all of a sudden, I saw another copy of that node again, floating there, smiling at me. I deleted it. Then later, there again... another one. Deleted it. Now it's been a whole day later, and I've closed and reopened the shader at least once or twice, and still from time to time that node appears, and I delete it. I even got all smart and figured I'd get rid of it by trying this... when the node appeared again, I connected the node into my main node, and plugged in all the required variables into the node, so that my shader would compile (green button in top left corner). Once done, then I deleted the node. I figured, I'm so smart, I got it that time. Nope, the node still reappears from time to time. I've tried to make the node appear on my command, but I can't figure out what makes it appear... and it's always appeared outside of my view, so I've yet to actually witness the mysterious event.