Regarding the fact that in Proof-of-Stake, a stakeholder will be elected randomly as the next author of the next block in each epoch (or each round or slot), logically, in each round (or slot) there is only a single author of block, and so a single proposed block. With these conditions, and whether this new block will be validate or not by the rest of the network, is there still the possibility of occurring a fork in each round? (As in each round a single author is selected.)
IMPORTANT : In this question, I mean "slot" by saying "round" and "epoch".
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Proof-of-Stake: How to prevent someone from being always selected as an author of block?