Simple. The sooner the better. In the workplace, procedures rule. Professionals who know their rights will move towards a grievance procedure in order to deal with an issue or behaviour that they consider to be wrong or unfair. However many people don't realise that Step 1 of most grievance procedures allows a space for those involved to seek an informal resolution. This is the time to call the mediator.
An impartial third person, the mediator who is not an employee of the company, will come to meet with the people involved, before statements are taken, lengthy third party interviews are held, transcripts of conversations paid for, management time devoted to something...that could be as simple as a small misunderstanding.
There is little to be gained for the employee having to go through the rigours of a formal process where swords are drawn and postions taken. These positions can become more entrenched as time passes.
As a former employment lawyer I have seen lengthy tribunal hearings take place due to a simple misunderstanding: 'he must have said/done that because he knew I was pregnant' for example.
Outcome: manager proved he did not know person was pregnant when the comment was made.
Company: large legal bill.
Employee, no job,
Team: ripples of disquiet spreading slowly from the epicentre.
What the manager said was not the best passing comment in the situation which springs to mind. And maybe if mediation had taken place he would have realised how he sounded from her perspective (with her recently discovered pregnancy very much on her mind.)
I imagine the conversation that could have taken place in mediation: surprise on his part, 'how could she have got it so wrong?'
Turning to 'Oh..so she thought...hmm..I see. well if she thought I knew that, no wonder she got so upset.How awful!' ...etcetc.
Then apologies, often on both sides and back to work with a little more care being taken over the inappropriate use of humour and some thought in place to avoid similar miscommunication taking place.