did you try the command console app for the input test ? and disable all the flow control flag like RTS/CTS .
Thank you for the suggestion. I tried it out and saw that it was not an SDK issue because the console app worked fine when encrypted.
I did some digging and found that the problem was the way my UART RX routine was coded. When I reverted back to wiced_uart_receive_bytes(), it worked fine with secure SFLASH enabled. Case closed!
thanks for the share..