The situation I would fear, which I perhaps described in too few details, would be the following:

Assume that for some reason, enough doubt was casted on a state's results by the Trump administration. In that case, the state legislature could invalidate the results and call the opposing party's set of electors to a vote. Even if it doesn't, the GOP could call its electors nonetheless, in a totally anticonstitutional way (but do they really care?).

What happens if two sets of electors vote separately and send competing lists to the VP? What would Pence do in that case?

I know this sounds silly, but seeing the precedents they have set, nothing would surprise me from the Trump administration. It would require the complicity of a state legislatures, which is not