Jalview always add updated SWISSMODEL models from 3D beacons

Swissmodel rebuilds models very regularly and 3d-beacons shows the latest models for a sequence. That means that when a 3d-beacons search is performed for a sequence that already has a swiss-model structure cached for it, 3d-beacons will show the updated model. Selecting the updated model to view will add it to the cached set of models - and there is no way of removing old models, so the cached model set will increase ad-infinitum.