Submitted by Shield, also found by zzebra83 and Tendency
https://github.com/code-423n4/2024-03-taiko/blob/main/packages/protocol/contracts/L1/libs/LibProving.sol#L219-L236 
https://github.com/code-423n4/2024-03-taiko/blob/main/packages/protocol/contracts/L1/libs/LibProving.sol#L389
In the LibProving.proveBlock function the top tier prover is allowed to prove a new transition as long as the new transition is different from the previous transition and assert conditional checks pass.
But the assert condition of this logic is wrong since it checks for the ts.contestBond == 0 where as it should be ts.contestBond == 1 since 1 is set as the default value for ts.contestBond parameter for gas savings as shown below:
As a result of the even though code expects the top-tier prover to re-prove a different transition, the transaction will revert.
Add the following testcase test_L1_GuardianProverCanOverwriteIfNotSameProof_test to the TaikoL1LibProvingWithTiers.t.sol test file.
If you change the ts.contestBond == 0
to ts.contestBond == 1 in the second assert statement of the LibProving.proveBlock function, the test will run successfully and transaction execution will succeed.
VSCode
Hence recommended to update the ts.contestBond == 0 in the second assert statement to ts.contestBond == 1 in the LibProving.proveBlock function.
dantaik (Taiko) confirmed and commented:
