Dealing with ISSU-SP-3-PEER IMAGE INCOMPATIBLE when the images are compatible

From Cisco Clue

Most likely you are also getting this:

%PFREDUN-SP-4-INCOMPATIBLE_ISSU_MATRIX: Compatibility Matrix check failed. reason 100

This is preventing you moving to SSO.

reason 100 refers to some configuration commands being mismatched between synchronised versions of the startup-config, use the command

redundancy config-sync validate mismatched-commands

to check which these are, fix them and then issue

show issu config-sync mismatched-commands

You are now ready to reload the standby.