> Conversely, letting them vest will send a message that this behavior is tolerated.
These are colleagues not children. Using threats will not have a good effect.
Also OP seems to have been tolerating their behavior, which sends the message that behavior will be tolerated. This is the right message to send as well.
We (and possible OP) don't know what the employee was going through, giving them lots of slack and support shows to the other employees that they will be supported. As well as just being a good thing to do, it will improve employee retention, effort, buy in to the company etc.
These are colleagues not children. Using threats will not have a good effect.
Also OP seems to have been tolerating their behavior, which sends the message that behavior will be tolerated. This is the right message to send as well.
We (and possible OP) don't know what the employee was going through, giving them lots of slack and support shows to the other employees that they will be supported. As well as just being a good thing to do, it will improve employee retention, effort, buy in to the company etc.