serial console not accepting input

I have an embedded Linux system (based on NXP imx53) with barebox loading Ubuntu 18.04.2 LTS with kernel 4.14.87-armv7-rt-x13

I have the serial console setup on /dev/ttymxc0

I see (via SSH) that there is agetty running on this port with the following parameters:

/sbin/agetty -o -p -- \u --keep-baud 115200,38400,9600 ttymxc0 vt220

Now, during the barebox part of the boot the console is working as expected, I get the output from barebox and can interact with it, input is accepted, no problem at all. When Linux is booted, I see all the boot output on the console and eventually get to a login prompt, however serial input (through putty) is not being received/accepted. Basically typing into the console does nothing at all. If I kill getty (by connecting via SSH) it is respawned and I see a new login prompt printed on the serial console but still my input is not accepted. If I start a reboot process (via SSH) I can see the shutdown messages on the serial console and when it reaches barebox I can interact with it over the serial console.

If I open minicom on /dev/ttymxc0 (again via SSH) whatever I type there gets output to the serial console but nothing appears in minicom if I type in the serial console

My guess at this point is that the console input is being redirected elsewhere, checking lsof shows /dev/ttymxc0 open by 3 agetty instances, is this normal?

# lsof | grep ttymxc0
agetty    5893            root    0u      CHR     207,16      0t0      11275 /dev/ttymxc0
agetty    5893            root    1u      CHR     207,16      0t0      11275 /dev/ttymxc0
agetty    5893            root    2u      CHR     207,16      0t0      11275 /dev/ttymxc0

I'm not sure where to look further into this problem so any suggestions are welcome.

Thanks

You might need "-L" on the agetty command to disable wait for carrier detect.

Moved: This thread is more suitable in <Linux - Embedded & Single-board computer> and has been moved accordingly to help your thread/question get the exposure it deserves.