As a safety mechanism some of the contracts are able to be paused if a hack, exploit, or bug is detected early enough. It can only pause the protocol, and the pauseGaurdian is DAO changeable.
Relevant Addresses:
Ethereum
Optimism
3 of 6 opMultiSig: 0x652AbFA76d8Adf89560f110322FC63156C5aE5c8 2.
