SSH login to cygwin sshd (6.7p1-1) fails with error seteuid1000: Operation not permitted when ~/.ssh/id_rsa keys available on client

[The Sec Maestro]

SSH Login, using 'tester' account (in Adminstrators group) to the Cygwin
sshd server fails from a client machine which has ~/.ssh/id_rsa keys
available.

Login from the same client, without the id_rsa keys is successful. SSH
locally (on cygwin box) is also successful.

Comparison of the sshd logs (debugging enabled) of a good vs failure login
shows that when id_rsa is enabled on the client, the following in the
failure case:  

debug1: temporarily_use_uid: 1000/513 (e=18/544)
seteuid 1000: Operation not permitted

This seem to be related to a permission related problem, but cygcheck_output
though shows the 'tester' user is member of Administrators group.

What I am I missing?

Thanks,

Novice Cygwin user

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