MS 210 & MS 225 switch models root bridge

[Jobsp]

I had an issue recently where 3 switches were stacked together earlier like below? 

1) MS225-48FP (At top)

2) MS210-48  (Middle)

3) MS225-48FP (At bottom)

It was working fine until the bottom switch got dead one day, and I replaced with another switch of same model, the moment I connected the replacement switch the entire network building got flapping and the network went down, when I removed the replacement switch the network became up. 

All the above stacked switches are connected to 2 distribution switch (Cisco 9300)  which are also stacked.

What is the reason for this network to go down? Is it due to root bridge election? or due to faulty replacement switch (but its a brand new one which was under warranty which was under RMA)?

[alemabrahao]

Did you follow this guide?

https://documentation.meraki.com/MS/Stacking/Switch_Stacks#Replacing_and_Cloning_Stack_Members

[KinaB]

Hello @Jobsp 

This could happen if the bottom switch was "Active switch" member. Please find this below document helpful: https://documentation.meraki.com/MS/Stacking/Switch_Stacks#Replacing_a_Stack_Member

" If the Active stack member is replaced there will be a short loss in connectivity when it is powered down while a new Active member is elected".