The party sending the file has asked if there is a way for them to identify
Hopefully, they have a unix sysadmin that can answer this for their system. . .
Long ago (early/mid-90's), when i doubled between mainframe and unix (was a dba on the mainframe and dba/sysadmin on unix), we used the "compress" unix command (which was part of unix). There were other ways (i.e. pkzip) that were licensed products. I don't recall having a "zip" command available, but it may well have been added.
All but 2 of them have the correct AUTO CRLF.
This may be due to the way these files are created on the unix system rather than a compression or file transfer problem. We had an XD command that produced a hex dump of a file - if the output of the xd is piped to "more", it can be viewed on their screen. Possibly they can see the difference between a "good" file and one that is not working.