How do I "fix" SSH_AUTH_SOCK?

[Jim Reisert AD1C]

I'm having a new, little problem with ssh. I can connect to my remote
host just fine if I use a Cygwin Terminal (mmtty).  I can not connect
in an Xterm without being prompted to enter a password:

    [JJR:~] $ ssh <remotehost>
    sign_and_send_pubkey: signing failed for RSA
"/cygdrive/d/Home/.ssh/id_rsa" from agent: agent refused operation
    (ad1ccus1@ftp.ad1c.us) Password:

I have determined that the environment variable SSH_AUTH_SOCK (bash
shell) seems to be causing this problem.  If I unset the variable,
then the remote connection in the Xterm works the same way as it does
using the Cygwin Terminal (i.e. no prompt for password).

This is the version of Cygwin/X I am running:

    Welcome to the XWin X Server
    Vendor: The Cygwin/X Project
    Release: 1.20.13.0
    OS: CYGWIN_NT-10.0-22000 JJR 3.3.0-341.x86_64 2021-09-24 22:07 UTC x86_64
    OS: Windows 10  [Windows NT 10.0 build 22000] (Win64)
    Package: version 1.20.13-1 built 2021-09-25

I will also add that I did not see this problem before updating to the
latest version of OpenSSH:

    OpenSSH_8.8p1, OpenSSL 1.1.1l  24 Aug 2021

However, the remote server had been running a very old version of
OpenSSH (circa 2013/2014).  They moved me to a newer server with this
version (obviously not the latest):

    OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017

Is there a workaround for this issue?

Thanks - Jim

-- 
Jim Reisert AD1C, <jjreisert@alum.mit.edu>, https://www.ad1c.us