MCUBoot serial download mode entry with CTS/RTS pin?

Dear community,

I am evaluating the nrf52 chip on the nrf52dk. I am using the peripheral_uart example, built for nrf52810. I have stumbled upon an error which I'm not sure how to resolve.

I want to perform a firmware update via MCUboot, but I only have connected the UART pins to the host MCU. I noted that the mcumgr util doesn't use CTS or RTS pins while transferring the new application image, I decided to use the CTS pin as the gpio to enter the MCUboot's serial downloader mode. 

However, when I flash the application on the chip on the nrf52dk, the application doesn't start correctly upon resetting the board. It only starts executing the application when I completely unpower and repower the DK. I see this problem dissapearing when I use some other GPIO on the DK (such as Button 1).

What could be the issue? Hope someone can help.

NB! I want to note that MCUboot's serial entry works with this CTS pin. FW update works too.

With regards,

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