Im not sure whats going on here either, I'll try look into it more. The spikes are all legitimate edits, I have been importing a lot of LINZ buildings recently, and have creates a pretty fast workflow for verifiying them. What seems to have happened is that mapwithai josm plugin has added source=esri to the nodes on new buildings I've uploaded. These are all new nodes so it hasnt created any more edits than expected but im not sure why these nodes have had the source tag added.