Hi Neil,
I can verify that ndpsmb.dll 3.7.1 dated July 28, 2020 is in ArcaOS 5.0.6. I'm seeing the dates messed up, but the exact cause is unknown. I'll edit this message if I find the cause.
3.7.2 is out, maybe give that a try?
I went from 3.7.1 here to 3.7.2, no issues to report, but I wasn't specifically trying to address a particular problem as my OS/2 box is a CLIENT only to the LAN NAS box.