As an optimization, dependency graph evaluation skips through no-op nodes at the scheduling stage. However, that leaves update flags enabled on the node, and the most problematic one is the USER_MODIFIED flag, which get flushed to children every time the no-op node is tagged. This in turn can cause simulation caches downstream to be permanently stuck in an outdated state until the depsgraph is rebuilt and the stuck flag cleared out. Differential Revision: https://developer.blender.org/D16868