It would be very useful add this warning to rb400 series on download page.
We have many 411 with firmware 2.12 and RouterOS 5.16 and lower.
After upgrading to 5.19 or 5.20 = kernel failure.
On download page NO warning 
Thanks
There is no known issue in RouterBOOT that causes Kernel failure, that is why there is no such warning. Are you sure this is related to RouterBOOT? How did you test that?
Ale you sure so routerboot 2.12 works with RouterOS 5.19 and 5.20?
I have another experience. Later I post an extract from the console