Flysky FS-i6X not binding

[Wesbflyer]

I just received a new FS-i6X 10 channel transmitter, and went thru the Bind process on 4 FS-iA10B receivers. It all went well. However, when I tried to bind to my one FS-i6A 6 channel receiver, not so well. The bind process finished with Bind successful, but the receiver kept on slow flashing the LED. It did not bind, even after a dozen attempts. Am I doing something incorrectly?? This 6 channel RX worked fine with my FS-i6 six channel transmitter, but that TX just died so cant test again.