Did the old DemandTools (v2.xx, the one with the ’90s Windows 3 UI) have these bugs?
1] if
- I have a unique-indexed field and
- I tell DT to copy a losing record’s unique ID onto a winning record,
it deletes the losing record. . . even if I told it not to delete losing records
2] the FieldCopyUnique command fails to migrate certain values from losing records to winning records
- for me, it’s working with Text, but failing with URLs and Phone Numbers
UPDATE 2024-04-03: we think this problem was caused when by cloning one of DT’s pre-existing merge scenarios. If we build a scenario from scratch, FieldCopyUnique works properly.
Kudotek v2.0 
Here’s the problem I was wrestling with the previous week, where the “Blank Values” checkbox doesn’t work the way anyone would expect