Ok. So, the problem was in the mapping array in g_ADigitalPinMap[]. Remapping the pins solves the problem (see the code below).
#if defined(NRF52)
//#define NRF52_DISABLE_INT // Not recommended to enable
#include "nrf.h"
// Interrupt is only disabled if there is no PWM device available
// Note: Adafruit Bluefruit nrf52 does not use this option
#define NRF52_DISABLE_INT
const uint32_t g_ADigitalPinMap[] = {
// D0 - D7
11,
12,
13,
14,
15,
16,
17,
18,
// D8 - D13
19,
20,
22,
23,
24,
25,
// A0 - A7
3,
4,
28,
29,
30,
31,
5, // AIN3 (P0.05)
2, // AIN0 (P0.02) / AREF
// SDA, SCL
26,
27,
// RX, TX
8,
6
};
volatile NRF_PWM_Type* PWM[3] = {NRF_PWM0, NRF_PWM1, NRF_PWM2};
#endif