I manage a team of around 15 and have done so in my place of work for around 10 years. We have always been a close-knit team. One team member has sporadically made accusations against me of bullying. These have always been investigated and dismissed, because I have not done so. I am in a position now where I am basically afraid to pull her up on anything. She works well in most ways, but there are a few issues she struggles with that should be dealt with but are not. She does have a mental health diagnosis and allowances have been made.
Recently, there has been quite a bit of staff turnover (not just in my department, but in the organisation as a whole as well). Some new members of the department have buddied up with this person and gone to senior leadership complaining of various aspects of my leadership. The nature of these have changed over the course of a couple of weeks and have been dismissed by our line manager as baseless. However, the original team member lodged a grievance against me - this has never happened before as previous complaints have been informal. The grievance was very painful to read and was largely completely untrue and/or based on things that were outside my control. Several issues had been previously brought up and dismissed, often years ago. After I responded to the grievance, it was dropped by the team member.
This feels like bullying now. Would I be unreasonable to lodge a counter grievance and could I also complain about some of the newer members of the team, some of whom have told this person they have heard me make negative comments about her (I haven't) only to then say they can't remember any specifics when questioned. I just don't know how we can move forward from this unless this is dealt with head on.