While messing with my armor I tried to add the Traveler's Cloak of invisibility. It made my character invisible but not the armor itself, which kind of defeats the purpose when you want to jumpscare friends on your server.
I found illusivesoulworks/constructsarmory#97 which suggests more recent versions of conarm contain a bugfix for this issue. They are currently at Beta version 1.12.2-0.0.23-rc3.jar whereas sevtech 3.0.8 contains 1.12.2-0.0.21-rc1.

Thank you for this great modpack!

Constructs Armory will be updated in the next release of the pack.