Rex, I think you mentioned that COPY with a URL and COPY with IFTP used the same code. I believe that, but there must be some difference that makes the two behave differently (with active FTP). Below, COPY with IFTP fails to get all of one file and fails to get another altogether.
Thanks for testing, Jay. I saw the logs of your tests a few minutes afterward (and eagerly awaited your post, not wanting to scoop you). :-)
Apparently the problems you had were the same as mine. I can post server logs, but the errors have been posted ad nauseum already.
My original post had a typo; it should have read: With passive FTP turned off, I cannot copy the files from Vince's server or FROM my own. Just in case the problem was with Vince's server, I created a directory on my server, copied all the files to it, turned off passive FTP, and then tried downloading them. The attempted copy failed even worse in that case.
So it does appear that something changed between version 15 and version 16. Unless being able to copy in active FTP mode was a bug previously (and apparently with other FTP software), something seems to be wrong in the new version in TCC.