Page 770 [URL] you could try to increase the hello time of spanning tree to see if it will stop switching. 
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 0Po1 is transitioned from the Forwarding state to the Blocking state in instance 0I 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
Dell N4032F Po1 Learning to forwarding