  Ethereum has undergone a recent change called \textit{the Merge}, which made
Ethereum a Proof-of-Stake blockchain, shifting closer to BFT consensus.
Ethereum, which wished to keep the best of the two protocol designs (BFT and
Nakomoto-style), now has a convoluted consensus protocol as its core. The
result is a blockchain being possibly produced in a tree-like form while
participants try to finalize blocks. We categorize different attacks
jeopardizing the liveness of the protocol. The Ethereum community has responded
by creating patches against some of them. We discovered a new attack on the
patched protocol. To support our analysis, we propose a new high-level
formalization of the properties of liveness and availability of the Ethereum
blockchain, and we provide a pseudo-code. We believe this formalization to be
helpful for other analyses as well. Our results yield that the Ethereum
Proof-of-Stake has safety but only probabilistic liveness. The probability of
the liveness is influenced by the parameter describing the time frame allowed
for validators to change their mind about the current main chain.
