nrf52 serial port printf causes system hang

[shayo]

• Type: Critical bug
• Related issue: nRF51-DK printf() causes hang when PC serial port not active / not opened. mbed-os-example-ble#25
• Priority: Blocker

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Bug

I believe the same behavior (serial port not open on PC causing system hang) happens on nrf52 targets as well. As soon as I reach a printf, the cpu hang.
This was reproducible on nrf52DK when trying to open a second serial port on two random I/O pins.
Is there a workaround for nrf52? I saw the related issue on nrf51dk.
This did not pose a problem in older versions of mbed, but seems to be happening with mbed lib v144 (both OS2 and OS5).

Target
NRF52

Toolchain:
GCC_ARM / mbed online compiler

Expected behavior
System should not hang.

Actual behavior
System hangs.

[shayo]

Confirmed. Adding
"target_overrides": {
"NRF52_DK": {
"target.uart_hwfc": 0
}
To the mbed_app.json solves this problem.