Dell N4032F Po1 Learning to forwarding

Hi,

I got 2 switch N4032F stacked and my Po1 have some problem.

each seconde i got in log this :
Po1 is transitioned from the Learning state to the Forwarding state in instance 0
Po1 is transitioned from the Forwarding state to the Blocking state in instance 0

I got many Po1 with the same equipement connect in the same switch, with the same configuration. Why it happen just on this Po ?! Other equipement is a Mikrotik CCR1072.

Thank you