FTP uploads no longer work on changed/updated files

[Running DW v. 21.3 on Mac OS 12.4]

Hello. For three days, I've experienced unreliable FTP uploading. For no apparent reason, when I attempt to put [all small] files that haven't been changed or updated in the last three days, the uploads complete successfully.

But the uploading fails when I try to put files that I've changed or updated over the past three days. I continually receive the same error message: 

“Error occurred — An FTP error occurred — cannot put “currentMessageTheme-Romans.html.” Internal data error: Transferred file size does not match the expected file size.”

I've done numerous things to resolve the issue:

1.  I asked my host/server to inspect my cPanel settings and advise of problems or needed changes. The host/server found nothing on its ends but suggested that I try using Cyberduck or another free FTP client to see if the changed/updated files could upload on it. Cyberduck was able to upload the changed/updated files.

2.  I verified with my host/server that the settings I entered in DW's Manage Sites windows were correctly entered.

3.  I also set the FTP connection in DW to FTP over SSL/TLS (explicit encryption); the Port to "21"; and "Passive FTP."

4.  I quit DW, turned off my iMac, reactivate my iMac, and reopened DW. Still got the same error message when attempting to upload changed/updated files.

Because none of these efforts have been productive, I ask the DW Community to suggest what my next step should include.

Thanks, in advance. Lemmeeeeno if screenshots would be helpful.

Warren