LTM4622 start-up not monotonic

Hello,

we designed in LTM4622 uModule power supply, but during ramp-up we observe non-monotonic behavior. When Vout is ramping up, we see a small drop there.

-When we replace ferrite beads with 10mOhm sense resistor and calculate the output current, there is no significant current spike when the voltage drop is happening. Measured current is far below I lim

-We tried to experiment with various Css, from 0 to 100nF. The glitch always happens at similar voltage level

-This happens on two independent power rails, 1V2 and 1V5. The glitch always seems to happen at about 80% of Vout

-As can be seen from the scope snapshot, Vout is gradually increasing (I guess that is the soft start) but after the drop the rise seems to be smoother, suggesting that part goes to CCM at thet point?

-In schematics, SYNC/MODE is tied via 0R to GND to force CCM.We tried to pull SYNC/MODE to 3V3 and the glitch seem to disappear. Could the glitch be explained by part swicthing from SS to CCM mode?

-If SYNC/MODE is tied to 3V3, does it auromadtically disable Burst mode at higher loads?

Below is screenshot from 1V5 rail, with SYNC/MODE to GND. 1V2 behaves the same.

Any other deas how to troubleshoot this are welcome.

Thank you