Symptom
Steps to reoproduce:
Join AP to 9800
Go to Configuration > Access Points > click on the AP > High Availability
Configure primary WLC to be: WLC-1 192.168.1.100
Configure secondary WLC to be: WLC-2 192.168.1.200
SSH to the WLC and try to swap the primary and secondary from CLI. This scenario is very useful in situations where you would want to migrate multiple APs to a different WLC in batch. Run the commands to swap them:
ap name controller primary WLC-2 192.168.1.200
ap name 3702_zeinedesk controller secondary WLC-1 192.168.1.100
9800 will take in these commands without throwing any error, but the configuration on the AP will not change. The WLC should either throw the error saying "hey, this WLC is already secondary, command will not be accepted" or the WLC should do something and maybe swap the primary and secondary.
Conditions
tested on 17.3.1 and 16.12.4, probably affects other versions
Workaround
use a different method to move APs from one WLC to another in a batch
