MP2636GR undershoot problem

After I cut off Vin=5v [PowerON, battery connected chip] the chip experiences an undershoot. Is it normal, if not how can I resolve it?
VIN = 5V, CIN = CSYS = 22μF, L1 = 2.2μH, RS1 = 20mΩ, C4 = CTMR = 0.27μF
C2 =100μF , CBATT =10μF || 10μF, VBATT=3.7V, Iload=1A

Hello Hamidnz2 and welcome to the forum,
It’s possible that the voltage setting for PWIN is set too low, such that Vin dropping to a lower voltage prevents continuous power to the SYS. REview that setting and possibly lower Vin slowly to see the effect of the switchover at lower Vin falling rates.

The scope trace has a strange noisy characteristic, it should be constant, so you may want to adjust the probe connections (firm ground) or add filtering.