The use of block.timestamp in the _updateLock function for time-based comparisons can be problematic because miners can manipulate the timestamp to a certain degree. This manipulation could affect the logic that checks if a lock's expiry time has passed or if a new locking duration is valid.

Problematic Code:

To mitigate this risk, consider using block numbers for duration-based logic or an external time oracle for precise timestamps. Document the choice and ensure that the potential for minor timestamp manipulation is acceptable given the contract's use case.