Between existence and non-existence there is no mean. This principle is inviolable. To declare that something oscillates between existence and non-existence is illogical, and untrue.
Particles do not pop in and out of existence. The Universe does not pop in and out of existence.
Any theory of the Universe that contradicts that, is an invalid theory and untrue.
Maybe so. In that case, there is another plane of existence that we currently can’t view, that the energy that composes ‘potential particles’ lives in.