CPLL Failure to lock

Does anyone know what may cause a PLL lock failure if the device has the XTAL registers set? Currently using the DWM 3000 Eval board alongside the Arduino shield on a STM32. Any sources we can compare source to?

	write32bitReg(RF_CONF, RF_TX_CTRL_2, RF_TX_CTRL_2(config->channel));
	write16bitReg(FS_CTRL, PLL_CFG, PLL_CFG(config->channel));

	if (config->channel == 9) write32bitReg(RF_CONF, RF_RX_CTRL, 0x08B5A833);

	write8bitReg(RF_CONF, LDO_RLOAD, 0x14);
	write8bitReg(RF_CONF, RF_TX_CTRL_1, 0x0E);
	write8bitReg(FS_CTRL, PLL_CAL, 0x81);
	write8bitReg(GEN_CFG_AES_0, SYS_STATUS, 0x02);

	// Set state to IDLE
	write16bitReg(PMSC, CLK_CTRL, 0x200);
	or16bitReg(PMSC, SEQ_CTRL, 0x100);

	for (uint8_t i = 18; i; i--) {
		if (read8bitReg(GEN_CFG_AES_0, SYS_STATUS) & 0x02) break;

//		if (i == 1) Trap(); // stuck here