Tree traversal can be done many ways with potentially differing impacts on caching below.
Can you describe Duplicati visit by terminology in that article, or writing your own phrases?
My other worry is Channel Pipeline spreading access across time, maybe upsetting cache.
Does Duplicati test-filters command without filters do same walk as a regular backup?
If it hasn’t already been run, some pure walk like tree /f or Get-ChildItem might help inform.
NetWare is probably now used to seeing those run, so how exactly is Duplicati upsetting it?
What’s the difference in the total size, folder structure (name length, depth), anything else?
If some volumes work but Q: doesn’t then questions are why – then can we give any help?