Heroes 3 HD costume sets

[ranon20]

I am using Heroes 3 HD (HOTA) and am trying to use the feature of artifact sets (costumes)

When I set the costumes with CTRL-1 and CRTL-2, it works. For that turn also I able to swap the costumes.

However when I come back few turns later and try to swap the costumes, it gives a beep sound and does not work.

Can anyone tell me the probable reason for this? Maybe I am swapping the boots outside the costume (wayfarer and swift boots). Is that the issue?

Any help will be appreciated.