Same battery voltage reading, 3700mV, even though it charges

Hi all,
I am charging a 650mAh LiIon battery through a Q2400 module from a switching current source of 800mA, maximum voltage 4.8 Volts. I set the charging parameters as follows:
I’m starting the charging process as bellow:
Although the battery is charging correctly and its voltage rises slowly and with pulses, the AT+WBCM=2 always reports 3700 mVolts, even though the battery has reached 4200 mVolts. The battery is connected directly to the Vbatt pins of the GSM module using a short cable (3cm) so there is no issue of the cable resistance. Can anyone figure out what is wrong? I’ve tried another GSM module (Q2406B) and another battery with the same results.