I tested 8 samples and I found two of 8 does NOT terminate the charging even if VBAT reached 8.23V and the charge current decrease down to 50mA.
I attach my schematic , please advice me how to fix this problem.
When you say the charge current decreased down to 50mA, are you measuring across the sense resistor? A load across the battery can keep the charger in a "charging" state forever if C/10 is not reached. The /CHRG pin is only dependent on the C/10 threshold, even if timer termination is used.