Are ValueTrees threadsafe?

I'm trying to debug an intermittent and seldom occuring bug that may be happening when saving the ValueTree content to a stream using ValueTree::writeToStream. The save operation appear to become corrupted. I know that other threads may be writing to the ValueTree, possibly while writing to a stream. If this is the case, and the Tree isn't threadsafe, I assume the operation is busted.  Jules can you confirm if it is/isn't threadsafe?

Nope, definitely not thread-safe.