Conservation of energy is a "universal" law, and would be counterintuitive to have someone travelling from a universe like ours - with our physics framework - into another universe that obeyed other laws of other-physics.
So, if we keep that premise that a parallel universe accessible from ours has to be under our same laws of physics framework, to have someone or something travelling from our universe into it (and back from it into ours) would break energy conservation law as matter/energy would disappear from our universe and "be created" in another parallel universe.
I thought about a mandatory constraint that would kill someone - or "someones" - into the destination universe, but that is bad because it makes the universe "sentient" somehow and then it turns to crazy pseudoscience and not some "possible science" based on quantum speculation. Also, how would the origination universe replenish the energy/mass lost when the traveler left it.
Then, I had the idea to have a forceful exchange between a traveler and its counterpart on the destination universe. That is an amazing thing for storytelling, but creates another problem, wormholes are one-way only conduits meaning there is only one direction through the central singularity from the black hole to the white hole. That makes impossible to exchange subjects without another wormhole opened from the destination universe.
I am hitting my head against this roadblock in my worldbuilding now, as parallel universe traveling is the basis of all my stories.
What are some ways you would suggest that would make it possible to keep energy conservation universal constraint when a given mass travels from a parallel universe to another through a wormhole?