File transfers missing final bytes

On a Novell NetWare 4.11 WAN using IP and IPX, files being transferred to a couple of locations end up missing the final one or two bytes and thus end up unusable. We have 75 locations, most of which are on 56K leased lines. The problem locations are all on 56K leased lines.

Groupwise email seems to work fine across the WAN links, including attachments.

It's only files that are copied from one server or workstation to the NW server on the other end that cause problems. We've attempted copying by Windows Explorer, DOS copy and xcopy (with /v) and ncopy (also with /v). Nothing seems to work. All files copied end up missing the final one or two bytes. Using the /v with xcopy and ncopy show no errors, but the file isn't complete.