Date & Time: N/A, happens anytime.
Frequency: Happens every time I change to a job that is assigned an instant portrait, but only if they have armor pieces that they cannot equip on top of gear.
World name: Gilgamesh
Character name: Jennen Cori
Class/Level: All jobs, all levels. Item/glamour issue

Steps:
1. Apply glamour to armor set on one job using job specific equipment (Ex. Samurai)
2. Switch to job that uses same armor set that has instant portrait applied (Ex. Monk)
3. Portrait reports that gear is inconsistent with current set current gear set.
4. Portrait can be fixed by re-assigning instant portrait now that you are selected on the correct job, but will break again when you switch jobs.

Additional notes:
I have a Dark Knight portrait that also has job specific equipment glamour, but the glamour pieces are for Dark Knight and do not break instant portrait assignments.

On my MNK/SAM gear set, I have glamoured SAM only armor on body and legs, which I believe is breaking my Monk portrait. It is the same on my MCH portrait as I have BRD and DNC gear glamoured over some parts of my BRD/MNK/DNC gear set.

See image below.