It’s failing because you aren’t being precise enough with your tree structure. When you graft the V input, the value you have highlighted comes in at path {0;5;2}, and then you want to compare that to an item in branch {0;5}. The component wont know to compare these as they have different paths. When working with multi-layered trees, you need to take some time before running them through components to get the exact data tree structure in order.
I made a simple cluster for this exact issue a while back which should help you out:
DomainInclusionbug.gh (20.7 KB)