Players, particularly high-resonance ones (“whales”), are able to remove gear/gems to lower their resonance value in order to circumvent the vault matchmaking, and then equip just before the pvp begins which gives them an unbalanced advantage and defeats the whole point of the matchmaking design.
It’s easy to fix this loophole:
Upon entering the vault (Shadows), or upon queueing to defend (Immortals), the system should measure resonance for matchmaking and then not allow changes to equipped gear, including any equipped gems or legendary gems that affect resonance values.