Failure to sign a validator in 12 of the 24 most recent blocks is slashes with 1% of the total validator stake. That is, if the validator node is in the blockchain in an activated state (Set Online), but for some reason has not signed the blocks. For example, due to an unreliable Internet connection. 12 of 24 blocks in any order. The total amount of the stake includes all the funds delegated to this validator and his personal funds.
To prevent this slash's, Decimal has prepared a special service - Decimal Guard. Installation instructions are here. This service monitors the block signing process for a particular node and, if necessary, sends a Set Offline transaction that deactivates the masternode before it is penalized. Guard fires at the specified skip block threshold, which is configurable. The Set Offline transaction is created and signed in advance, and when Guard is triggered, it simply sends it to the network. The next deactivation will require a new transaction stored in Guard.